A173013 a(1) = 1, for n >= 2; a(n) = the smallest number h such that sigma(h) = A000203(h) = a(n-1) + 3, a(n) = 0 if no such number exists.

1, 3, 5, 7, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2

Offset

1,2

Comments

a(n) is eventually periodic sequence with period (0, 2).

Links

Table of n, a(n) for n=1..52.

Formula

A000203(a(n)) = a(n-1) + 3 for n >= 2.

Prog

(PARI) a(n)=if(n>4, 2-n%2*2, 2*n-1) \\ Charles R Greathouse IV, Feb 14 2013

Crossrefs

Cf. A000035, A173012, A173014, A173015, A173016.

Sequence in context: A004785 A099744 A024601 * A223174 A225401 A085090

Adjacent sequences: A173010 A173011 A173012 * A173014 A173015 A173016

Keyword

nonn,easy

Author

Jaroslav Krizek, Nov 06 2010

Status

approved