A053231 First differences between n for which sigma(n) < sigma(n+1), which are not 2.

1, 1, 4, 1, 1, 1, 1, 4, 4, 1, 1, 1, 1, 4, 1, 1, 4, 1, 1, 4, 4, 1, 3, 4, 4, 1, 1, 1, 3, 1, 1, 4, 1, 1, 1, 1, 4, 1, 3, 1, 1, 4, 1, 1, 4, 1, 1, 4, 1, 1, 1, 1, 1, 1, 1, 3, 4, 1, 1, 1, 1, 1, 3, 4, 1, 1, 1, 1, 4, 4, 1, 1, 4, 4, 1, 1, 1, 3, 4, 1, 1, 1, 1, 4, 1, 1, 1, 1, 4, 1, 3, 1, 3, 4, 4, 1, 1, 1, 1, 4, 1, 1, 4, 1, 1

Offset: 1

Author

Asher Auel, Jan 10 2000

Keywords

• nonn

Crossrefs

Cf. A000203, A053224, A053230, A053232, A053233, A053234, A053235, A053236, A053237.

Programs

Maple

with(numtheory): f := [seq( `if`((sigma(i+1) > sigma(i)),i,print( )), i=1..5000)];
seq( `if`(f[i+1] - f[i] <> 2,f[i+1] - f[i],print( )), i=1..2000);

Formula

The expansion of A053230 excluding 2's. a(n) = A053230(A053232(n)).