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#111 |
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"William"
May 2003
New Haven
2×7×132 Posts |
(20723+1153#)/20723
(29995+1153#)/29995 3^2121*26+1 Code:
(33431+1153#)/33431 (33205+1153#)/33205 (31691+1153#)/31691 (32929+1153#)/32929 (14001+1153#)/14001 (25715+1153#)/25715 (25813+1153#)/25813 (25863+1153#)/25863 (29427+1153#)/29427 (29491+1153#)/29491 (29045+1153#)/29045 (28153+1153#)/28153 (28207+1153#)/28207 (28741+1153#)/28741 (28815+1153#)/28815 (16769+1153#)/16769 (18905+1153#)/18905 (19757+1153#)/19757 (20345+1153#)/20345 (27805+1153#)/27805 (27389+1153#)/27389 (26567+1153#)/26567 (25197+1153#)/25197 (10807+1153#)/10807 (23483+1153#)/23483 (17593+1153#)/17593 (17323+1153#)/17323 (17169+1153#)/17169 (11623+1153#)/11623 (12013+1153#)/12013 (12233+1153#)/12233 (12565+1153#)/12565 (12921+1153#)/12921 (15953+1153#)/15953 (15611+1153#)/15611 (15163+1153#)/15163 (13243+1153#)/13243 (21471+1153#)/21471 (6715+1153#)/6715 (8857+1153#)/8857 (4465+1153#)/4465 (2455+1153#)/2455 (3059+1153#)/3059 (3097+1153#)/3097 (3741+1153#)/3741 (3937+1153#)/3937 (6031+1153#)/6031 (7015+1153#)/7015 (7439+1153#)/7439 (8213+1153#)/8213 (8299+1153#)/8299 (8441+1153#)/8441 (9031+1153#)/9031 (1005+1153#)/1005 (1271+1153#)/1271 (6743+1153#)/6743 (6837+1153#)/6837 (5533+1153#)/5533 (5217+1153#)/5217 (5257+1153#)/5257 (5371+1153#)/5371 (4697+1153#)/4697 (217+1153#)/217 (527+1153#)/527 (611+1153#)/611 (34465+1153#)/34465 (34505+1153#)/34505 (38141+1153#)/38141 (38683+1153#)/38683 (39697+1153#)/39697 Last fiddled with by wblipp on 2013-03-09 at 01:25 Reason: More added |
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#113 |
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Apr 2010
Over the rainbow
1010001010002 Posts |
23^4381-22 proven by N-1
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#114 |
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"William"
May 2003
New Haven
236610 Posts |
10^2292+99 proven by N+1
(9661^577-1)/9660 by N-1 Last fiddled with by wblipp on 2013-03-23 at 16:23 Reason: add second |
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#115 |
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"William"
May 2003
New Haven
2×7×132 Posts |
(2^7737*9-1)/17
(10^2342+17)/117 (1263^757-1)/1262 2^7807-31 (2^7814*65-1)/259 21^1786-20 (19^1848*20+1)/21 (7129^617-1)/7128 (2^8012*147+1)/589 |
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#116 |
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"William"
May 2003
New Haven
2·7·132 Posts |
10^3546-1001
52^2071-51 |
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#117 |
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"William"
May 2003
New Haven
2·7·132 Posts |
(275^881-1)/274
10^2149*5-49 2^7152-513 2^7155+33 (10^2154*26-23)/3 |
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#118 |
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"William"
May 2003
New Haven
2×7×132 Posts |
The first one here was especially fun. Somebody had already tried the N-1 proof with inadequate factorization, but had missed the N+1 also had algebraic factors.
(10^2566*2-11)/9 (439^961+1)/(439^31+1) 10^2568*22-31)/9 (830^881-1)/829 |
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#119 |
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Apr 2013
Germany
1001101112 Posts |
That could have been me, as I tried this out a week ago or so (can't remember the numbers). What's the secret of finding easy ones? All I found needed some real strong sieving in order to factorize. I thought the easy factors are already tested by factordb.
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#120 |
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Apr 2010
Over the rainbow
260010 Posts |
if you find a prime in the form of
(a^x-1)/(a-1) or a^x-(a-1) or a^x-(a+1) those 3 are easy. |
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#121 |
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"William"
May 2003
New Haven
2×7×132 Posts |
The factordb does a poor job of finding algebraic factors, so I'm mostly spotting cases that have these algebraic factors. I pick a size and list 100 to 1000 PRPs starting at the size from here. Then I scan down the list, looking for numbers with small divisors, such as (10^2566*2-11)/9. The +1 and -1 will have terms that are constant + and - divisor. In this case 11+9 and 11-9. I then do mental arithmetic to see if the result will cancel the factor and or powers. This case was very special because 11+9=2*10 and 11-9=2, so both the sides end up with 10^n-1. If the calculations exceed my rather limited mental math abilities, I move on the the next one.
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