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Search: id:A129755
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| A129755 |
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Triangular numbers t such that t+10 is a prime. |
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+0
5
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| 1, 3, 21, 91, 153, 171, 231, 253, 561, 741, 1081, 1653, 1711, 1891, 2211, 2701, 3321, 3403, 4851, 6441, 8001, 9453, 9591, 10153, 12403, 15051, 16471, 17391, 18721, 23653, 24753, 27261, 30381, 32131, 35511, 38781, 39621, 41041, 44253, 45753, 51681, 55611, 56953
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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The only triangular numbers t such that t-10 is a prime are 15 and 21.
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MAPLE
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t1:=[]; f:=n->n*(n+1)/2; for n from 1 to 1000 do if isprime(f(n)+10) then t1:=[op(t1), f(n)]; fi; od: t1; [from N. J. A. Sloane (njas(AT)research.att.com), Jun 01 2007]
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MATHEMATICA
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Select[Table[n(n+1)/2, {n, 400}], PrimeQ[ #+10]&]
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PROGRAM
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(PARI) for(k=1, 100, t=(k*(k+1))/2; if(isprime(t+10), print1(t, ", "))) [from Joerg Arndt, Jun 01 2007]
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CROSSREFS
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Sequence in context: A034490 A071351 A083231 this_sequence A059826 A108970 A069017
Adjacent sequences: A129752 A129753 A129754 this_sequence A129756 A129757 A129758
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KEYWORD
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nonn
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), May 15 2007
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EXTENSIONS
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Checked by N. J. A. Sloane (njas(AT)research.att.com), Jun 01 2007
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