A173012 a(1) = 1, for n >= 2; a(n) = the smallest number h such that sigma(h) = A000203(h) = a(n-1) + 2, a(n) = 0 if no such number exists.

1, 2, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Offset

1,2

Comments

a(1) = 1, a(2) = 2, a(3) = 3, a(n) = 0 for n >= 4.

Links

Table of n, a(n) for n=1..69.

Formula

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

Prog

(PARI) a(n)=if(n>3, 0, n) \\ Charles R Greathouse IV, Feb 14 2013

Crossrefs

Cf. A000035, A173013, A173014, A173015, A173016.

Sequence in context: A013510 A013504 A230807 * A083925 A208150 A045830

Adjacent sequences: A173009 A173010 A173011 * A173013 A173014 A173015

Keyword

nonn,easy

Author

Jaroslav Krizek, Nov 06 2010

Status

approved