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A271319 Number of distinct prime factors of the n-th n-gonal number (A060354). 4
1, 2, 1, 2, 3, 2, 2, 2, 3, 3, 3, 2, 3, 4, 2, 2, 3, 4, 3, 3, 3, 3, 3, 2, 4, 3, 3, 2, 5, 3, 2, 4, 3, 4, 3, 2, 4, 4, 4, 3, 4, 3, 3, 3, 3, 4, 3, 2, 4, 4, 4, 2, 4, 4, 3, 4, 3, 3, 4, 4, 3, 5, 2, 3, 4, 4, 4, 4, 4, 3, 4, 2, 4, 5, 3, 3, 4, 3, 4, 3, 4, 4, 5, 4, 3, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

Colin Barker, Table of n, a(n) for n = 2..1000

FORMULA

a(n) = A001221(A060354(n)).

EXAMPLE

a(7) = 2 because A060354(7) = 112 = 2^4 * 7^1.

PROG

(PARI)

pg(m, n) = (n^2*(m-2)-n*(m-4))/2 \\ n-th m-gonal number

a(n) = omega(pg(n, n))

vector(100, n, n++; a(n))

CROSSREFS

Cf. A001221, A060354, A271320, A271321, A271322.

Sequence in context: A233519 A192295 A037195 * A319178 A254041 A240712

Adjacent sequences:  A271316 A271317 A271318 * A271320 A271321 A271322

KEYWORD

nonn

AUTHOR

Colin Barker, Apr 04 2016

STATUS

approved

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Last modified October 20 21:31 EDT 2020. Contains 337909 sequences. (Running on oeis4.)