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A216390
Number of values of k for which sigma(k) is a permutation of decimal digits of k, for 10^(n-1) < k < 10^n.
0
1, 1, 5, 10, 47, 200, 842, 4698, 28831
OFFSET
1,3
FORMULA
a(n) = # { k in A115920 | 10^(n-1) < k < 10^n }. - M. F. Hasler, Feb 24 2014
EXAMPLE
a(3) = 5 because the values of k satisfying the condition for 10^2 < k < 10^3 are {258, 270, 276, 609, 639}. - V. Raman, Feb 18 2014
PROG
(PARI) a(n)=sum(k=10^(n-1), 10^n, vecsort(digits(k)) == vecsort(digits(sigma(k)))) \\ V. Raman, Feb 18 2014, based on edits by M. F. Hasler
CROSSREFS
Sequence in context: A035406 A103932 A034190 * A305476 A270089 A336582
KEYWORD
nonn,base,more
AUTHOR
V. Raman, Sep 06 2012
EXTENSIONS
a(9) from Jinyuan Wang, Mar 02 2020
STATUS
approved