A028836 - OEIS

A028836

Iterated sum of digits of n is a power of 2.

1, 2, 4, 8, 10, 11, 13, 17, 19, 20, 22, 26, 28, 29, 31, 35, 37, 38, 40, 44, 46, 47, 49, 53, 55, 56, 58, 62, 64, 65, 67, 71, 73, 74, 76, 80, 82, 83, 85, 89, 91, 92, 94, 98, 100, 101, 103, 107, 109, 110, 112, 116, 118, 119, 121, 125, 127, 128, 130, 134, 136, 137, 139, 143, 145, 146, 148, 152, 154, 155

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..70.

FORMULA

Conjectures from Colin Barker, Feb 10 2020: (Start)

G.f.: x*(1 + x + 2*x^2 + 4*x^3 + x^4) / ((1 - x)^2*(1 + x)*(1 + x^2)).

a(n) = a(n-1) + a(n-4) - a(n-5) for n>5.

(End)

This g.f. follows from the observation that a(n+4) = a(n)+9 and this holds since the iterated sum of digits of N equals the iterated sum of digits of N+9. - Peter Bala, Feb 10 2020

CROSSREFS

Cf. A010888, A028838, A028889.

Sequence in context: A247324 A043706 A296691 * A028838 A178332 A265155

Adjacent sequences: A028833 A028834 A028835 * A028837 A028838 A028839

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Scott Lindhurst (ScottL(AT)alumni.princeton.edu)

Checked by Neven Juric (neven.juric(AT)apis-it.hr), Feb 04 2008

STATUS

approved