A080571 Number of 2's in partition of n-th Ulam number into sum of two distinct Ulam numbers.

0, 1, 1, 1, 2, 3, 4, 5, 6, 7, 10, 11, 14, 15, 18, 18, 20, 21, 24, 26, 27, 29, 31, 33, 37, 38, 39, 40, 43, 47, 50, 53, 55, 56, 59, 66, 67, 68, 69, 72, 75, 78, 79, 83, 84, 90, 91, 92, 93, 96, 98, 99, 104, 107, 118, 120, 121, 123, 128, 129, 136, 137, 138, 141, 146, 149, 153, 154

Offset

1,5

Links

Table of n, a(n) for n=1..68.

Example

For n=7: A002858(7) = 11 = 3+8 = (1+2)+(2+6) = (1+2)+(2+(2+4)) = (1+2)+(2+(2+(1+3))) = (1+2)+(2+(2+(1+(1+2)))). Number of 2's in (1+2)+(2+(2+(1+(1+2)))) is 4, so a(7) = 4.

Crossrefs

Cf. A002858.

Sequence in context: A251595 A373789 A050725 * A165805 A319975 A307625

Adjacent sequences: A080568 A080569 A080570 * A080572 A080573 A080574

Keyword

easy,nonn

Author

Naohiro Nomoto, Feb 22 2003

Status

approved