A216392 - OEIS

A216392

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

1, 1, 1, 1, 1, 1, 2, 2, 5, 7, 7, 13, 16, 21, 35, 57, 83, 143, 207, 278, 457, 790, 1064, 1815, 3468, 5194, 8226

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OFFSET

1,7

LINKS

FORMULA

a(n) = # { k in A115920 | k < 2^n }. - M. F. Hasler, Feb 24 2014

EXAMPLE

a(10) = 7 because the values of k satisfying the condition for k < 2^10 are {1, 69, 258, 270, 276, 609, 639}. - V. Raman, Feb 18 2014

PROG

(PARI) a(n)=sum(k=1, 2^n, vecsort(digits(k)) == vecsort(digits(sigma(k)))) \\ V. Raman, Feb 18 2014, based on edits by M. F. Hasler

CROSSREFS

KEYWORD

nonn,base,more

AUTHOR

V. Raman, Sep 06 2012

STATUS

approved