0,2

a(p^r) = prime(p)^r, p is a prime.

Table of n, a(n) for n=0..10.

a(4) = 49 as 4 = 2^2 = p^2 and the numbers of the form p^2 are 4,9,25,49,121,... and 49 is the 4th such number. a(6) = 22 = p*q, 22 is the 6th number in the sequence 6,10,14,15,21,22,26,...

Sequence in context: A227743 A235356 A120426 * A196467 A219506 A171775

Adjacent sequences: A077198 A077199 A077200 * A077202 A077203 A077204

more,nonn

Amarnath Murthy, Nov 02 2002

approved