OFFSET
1,2
COMMENTS
The only triangular numbers t such that t-10 is a prime are 15 and 21.
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
KEYWORD
nonn
AUTHOR
Zak Seidov, May 15 2007
EXTENSIONS
Checked by N. J. A. Sloane, Jun 01 2007
STATUS
approved