A359193 a(n) is the index of the smallest square pyramidal number with exactly n prime factors (counted with multiplicity).

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

Table of n, a(n) for n=0..34.

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

Cf. A000330, A001222, A359192.

Sequence in context: A098010 A088533 A091155 * A355457 A254432 A027362

Adjacent sequences: A359190 A359191 A359192 * A359194 A359195 A359196

Keyword

nonn,more

Author

Ilya Gutkovskiy, Dec 19 2022

Extensions

a(26)-a(34) from Daniel Suteu, Dec 29 2022

Status

approved