A080573 - OEIS

A080573

Number of ways writing n as a sum of two distinct Ulam numbers.

0, 0, 1, 1, 2, 1, 2, 1, 2, 2, 1, 2, 1, 3, 2, 1, 3, 1, 4, 2, 2, 2, 0, 3, 0, 1, 2, 1, 4, 2, 2, 2, 0, 3, 0, 1, 2, 1, 4, 2, 2, 3, 0, 4, 0, 2, 1, 1, 4, 2, 3, 2, 1, 5, 2, 3, 1, 2, 3, 2, 3, 1, 3, 5, 3, 4, 0, 2, 1, 3, 2, 1, 5, 3, 5, 2, 1, 3, 2, 4, 2, 1, 5, 2, 6, 2, 1, 5, 2, 5, 2, 0, 4, 0, 6, 0

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OFFSET

1,5

COMMENTS

After about 10^5 terms, the plot of this sequences begins to show some structure. - T. D. Noe, Jan 21 2008

When a(n)=1, n is an Ulam number, A002858. A033629 has the terms when a(n)=0. - Jud McCranie, Jul 22 2012

LINKS

T. D. Noe, Table of n, a(n) for n=1..10000

T. D. Noe, Plot of 10^5 terms of A080573

Rémy Sigrist, Density plot of the first million terms

Rémy Sigrist, C program for A080573

PROG