OFFSET
1,6
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
EXAMPLE
a(24) = 5 because divisors of 24 of the form "p*pp" are 2 = 2*1, 3 = 3*1, 8 = 2*4, 12 = 3*4 and 24 = 3*8 where 2, 3 are primes and 1, 4, 8 are perfect powers.
For n = 72, because divisors of 72 of the form "p*pp" are 2 = 2*1, 3 = 3*1, 8 = 2*(2^2), 12 = 3*(2^2), 18 = 2*(3^2), 24 = 3*(2^2) and 72 = 2*(6^2), a(72) = 7. The other five divisors of 72: 1, 4, 6, 9 and 36 are not of the required type. - Antti Karttunen, May 28 2017
PROG
(PARI) ispp(n) = (n==1) || ispower(n);
isA245303(n) = {my(f = factor(n)); for (i=1, #f~, p = f[i, 1]; if (ispp(n/p), return(1)); ); return (0); }
a(n) = sumdiv(n, d, isA245303(d)); \\ Michel Marcus, Aug 08 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Jul 28 2014
EXTENSIONS
Data section extended to 120 terms (with corrected term a(72), computed with PARI-program of Michel Marcus) by Antti Karttunen, May 28 2017
STATUS
approved