A033618 - OEIS

A033618

Number of ways n-th repdigit number, A010785(n), can be expressed as a polygonal number.

2, 2, 2, 2, 3, 2, 2, 3, 2, 3, 3, 2, 4, 5, 2, 3, 3, 4, 3, 4, 3, 4, 5, 3, 3, 3, 3, 2, 3, 3, 3, 6, 3, 2, 3, 2, 3, 3, 3, 3, 4, 2, 3, 3, 7, 3, 4, 3, 4, 5, 4, 3, 4, 2, 2, 3, 3, 3, 4, 3, 3, 3, 3, 4, 3, 2, 3, 6, 2, 3, 3

(list; graph; refs; listen; history; text; internal format)

OFFSET

2,1

LINKS

Table of n, a(n) for n=2..72.

M. Keith, On Repdigit Polygonal Numbers, J. Integer Sequences, Vol. 1, 1998, #6.

EXAMPLE

The n-th k-sided polygonal number is P(n,k)=n((k-2)n+4-k)/2 (k >= 2, n >= 1). For each repdigit number R>=2, sequence gives number of (n,k) such that P(n,k)=R.

CROSSREFS

Sequence in context: A234092 A047931 A258571 * A061357 A270966 A138139

Adjacent sequences: A033615 A033616 A033617 * A033619 A033620 A033621

KEYWORD

nonn,base

AUTHOR

Mike Keith

STATUS

approved