A173014 a(1) = 1, for n >= 2; a(n) = the smallest number h such that sigma(h) = A000203(h) = a(n-1) + 4, a(n) = 0 if no such number exists.

1, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7

Offset: 1

Author

Jaroslav Krizek, Nov 06 2010

Keywords

• nonn
• easy

Comments

a(1) = 1, a(n) = periodic sequence with period (0, 3, 4, 7) for n >= 2.

Crossrefs

Cf. A000035, A173012, A173013, A173015, A173016.

Programs

Mathematica

PadRight[{1},80,{7,0,3,4}] (* Harvey P. Dale, May 09 2012 *)

PARI

a(n)=if(n>1,[4, 7, 0, 3][n%4+1],1) \\ Charles R Greathouse IV, Feb 19 2013

Formula

A000203(a(n)) = a(n-1) + 4 for n >= 2.