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

Offset: 1

Author

V. Raman, Sep 06 2012

Keywords

• nonn
• base
• more

Examples

			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
		

Crossrefs

Cf. A115920, A000203.

Programs

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

Formula

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