A085783 - OEIS

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

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OFFSET

1,1

LINKS

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

EXAMPLE

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

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

CROSSREFS

Cf. A000040, A000217.

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

Sequence in context: A007071 A242482 A085784 * A143664 A282131 A114148

Adjacent sequences: A085780 A085781 A085782 * A085784 A085785 A085786

KEYWORD

nonn

AUTHOR

Jon Perry, Jul 23 2003

EXTENSIONS

107 and 109 inserted by Robert Israel, May 15 2018

STATUS

approved