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A359193
a(n) is the index of the smallest square pyramidal number with exactly n prime factors (counted with multiplicity).
2
1, 2, 3, 4, 7, 15, 24, 31, 63, 80, 175, 255, 511, 1023, 512, 6912, 2047, 6655, 14336, 16384, 32767, 90112, 131071, 180224, 483327, 1114112, 1638400, 2097151, 1048575, 16777216, 8388607, 33357824, 16777215, 92274687, 67108864
OFFSET
0,2
LINKS
Eric Weisstein's World of Mathematics, Prime Factor
Eric Weisstein's World of Mathematics, Square Pyramidal Number
PROG
(PARI) sp(n) = n*(n+1)*(2*n+1)/6; \\ A000330
a(n) = my(k=1); while (bigomega(sp(k)) != n, k++); k; \\ Michel Marcus, Dec 20 2022
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Ilya Gutkovskiy, Dec 19 2022
EXTENSIONS
a(26)-a(34) from Daniel Suteu, Dec 29 2022
STATUS
approved