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 A129755 Triangular numbers t such that t+10 is a prime. 4
 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; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The only triangular numbers t such that t-10 is a prime are 15 and 21. LINKS MAPLE 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 MATHEMATICA Select[Table[n(n+1)/2, {n, 400}], PrimeQ[ #+10]&] PROG (PARI) for(k=1, 100, t=(k*(k+1))/2; if(isprime(t+10), print1(t, ", "))) \\ Joerg Arndt, Jun 01 2007 CROSSREFS Sequence in context: A034490 A071351 A083231 * A059826 A108970 A069017 Adjacent sequences:  A129752 A129753 A129754 * A129756 A129757 A129758 KEYWORD nonn AUTHOR Zak Seidov, May 15 2007 EXTENSIONS Checked by N. J. A. Sloane, Jun 01 2007 STATUS approved

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Last modified October 23 03:21 EDT 2019. Contains 328335 sequences. (Running on oeis4.)