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A216393 Number of values of k for which sigma(k)-k is a permutation of decimal digits of k, for k < 2^n. 0

%I

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

%T 3611,6311,9674

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

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

%e 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

%o (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

%Y Cf. A085844, A001065.

%K nonn,base,more

%O 1,5

%A _V. Raman_, Sep 06 2012

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Last modified September 23 04:54 EDT 2020. Contains 337295 sequences. (Running on oeis4.)