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A129755
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Triangular numbers t such that t+10 is a prime.
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4
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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
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OFFSET
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1,2
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COMMENTS
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The only triangular numbers t such that t-10 is a prime are 15 and 21.
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LINKS
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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; # N. J. A. Sloane, 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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PROG
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(PARI) for(k=1, 100, t=(k*(k+1))/2; if(isprime(t+10), print1(t, ", "))) \\ Joerg Arndt, Jun 01 2007
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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