A216393 - OEIS

A216393

Number of values of k for which sigma(k)-k is a permutation of decimal digits of k, for k < 2^n.

0, 0, 1, 1, 2, 2, 2, 2, 4, 5, 6, 8, 13, 17, 32, 47, 63, 98, 189, 279, 437, 782, 1368, 2062, 3611, 6311, 9674

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,5

LINKS

Table of n, a(n) for n=1..27.

FORMULA

a(n) = # { k in A085844 | k < 2^n }. - M. F. Hasler, Feb 24 2014

EXAMPLE

a(12) = 8 because the values of k satisfying the condition for k < 2^12 are {6, 28, 411, 496, 604, 1305, 3664, 4086}. - V. Raman, Feb 18 2014

PROG

(PARI) a(n)=sum(k=1, 2^n, vecsort(digits(k)) == vecsort(digits(sigma(k)-k))) \\ Use digits(n)=eval(Vec(Str(n))) in old versions of PARI. - V. Raman, Feb 18 2014, edited by M. F. Hasler, Feb 24 2014

CROSSREFS

Cf. A085844, A001065.

Sequence in context: A046768 A363405 A274151 * A045812 A064877 A008363

Adjacent sequences: A216390 A216391 A216392 * A216394 A216395 A216396

KEYWORD

nonn,base,more

AUTHOR

V. Raman, Sep 06 2012

STATUS

approved