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A089136
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Primes in the progression (n! + m)/m where n advances by 1 and m resets to 1 upon each prime occurrence.
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2
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2, 3, 7, 13, 61, 241, 2521, 20161, 72577, 604801, 39916801, 59875201, 3113510401, 17435658241, 186810624001, 10461394944001, 118562476032001, 246245142528001, 24329020081766401, 304112751022080001
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Comment from Martin Fuller (martin_n_fuller(AT)btinternet.com), Apr 26 2007: Both this sequence and A092965 involve the largest prime of the form (n!/m)+1 but they differ in the allowed values of m. The present sequence allows any integer m dividing n!. But A092965 requires m to be the product of distinct numbers up to n. I believe that the sequences differ at n=104 and n=106: a(104)=(104!/121)+1, A092965(104)=(104!/266)+1, a(106)=(106!/121)+1, A092965(106)=(106!/133)+1.
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LINKS
| Martin Fuller, Table of n, a(n) for n = 1..200
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EXAMPLE
| n=7,m=1, (7!+ 1)/1 = 5041 not prime, m advances to 2, (7!+2)/2 = 2521 prime keep it. n advances to 8 and m resets to 1. (8!+ 1)/1 = 61*661 not prime. m advances to 2. (8!+2)/2 = 20161 prime keep it n advances to 9 etc
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PROG
| (PARI) nfactp2d2(n, m) = { for(x=1, n, for(k=1, m, y=floor((x!+ k)/k); if(isprime(y), print1(y", "); break) ) ) }
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CROSSREFS
| Different from A092965 (see Comments).
Sequence in context: A104372 A092969 * A092965 A051454 A051452 A058017
Adjacent sequences: A089133 A089134 A089135 * A089137 A089138 A089139
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KEYWORD
| base,easy,nonn
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AUTHOR
| Cino Hilliard (hillcino368(AT)gmail.com), Dec 05 2003
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