OFFSET
0,2
LINKS
Eric Weisstein's World of Mathematics, Prime Factor
Eric Weisstein's World of Mathematics, Square Pyramidal Number
EXAMPLE
a(4) = 140, because 140 is a square pyramidal number with 4 prime factors (counted with multiplicity) {2, 2, 5, 7} and this is the smallest such number.
PROG
(PARI) sp(n) = n*(n+1)*(2*n+1)/6; \\ A000330
a(n) = my(k=1); while (bigomega(sp(k)) != n, k++); sp(k); \\ Michel Marcus, Dec 20 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Dec 19 2022
STATUS
approved