A129755 Triangular numbers t such that t+10 is a prime.

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

Offset: 1

Author

Zak Seidov, May 15 2007

Keywords

• nonn

Comments

The only triangular numbers t such that t-10 is a prime are 15 and 21.

Crossrefs

Intersection of A000217 and A172407.

Programs

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]&]

PARI

for(k=1, 100, t=(k*(k+1))/2; if(isprime(t+10), print1(t, ", "))) \\ Joerg Arndt, Jun 01 2007

Extensions

Checked by N. J. A. Sloane, Jun 01 2007