A085783 Product of a prime and a triangular number.

2, 3, 5, 6, 7, 9, 11, 12, 13, 15, 17, 18, 19, 20, 21, 23, 29, 30, 31, 33, 37, 39, 41, 42, 43, 45, 47, 50, 51, 53, 56, 57, 59, 61, 63, 66, 67, 69, 70, 71, 72, 73, 75, 78, 79, 83, 84, 87, 89, 90, 93, 97, 101, 102, 103, 105, 107, 108, 109, 110, 111

Offset: 1

Author

Jon Perry, Jul 23 2003

Keywords

• nonn

Examples

			15 = 5*t(2) is a term.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040, A000217.

A196421 is a subsequence. - Michel Marcus, May 15 2018

Programs

Maple

N:= 200: # for all terms <= N
T:= [seq(i*(i+1)/2,i=1..floor((sqrt(4*N+1)-1)/2))]:
P:= select(isprime,[2,seq(i,i=3..N,2)]):
sort(select(`<=`,convert({seq(seq(p*t,p=P),t=T)},list),N)); # Robert Israel, May 15 2018

Extensions

107 and 109 inserted by Robert Israel, May 15 2018