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%I #6 Nov 22 2019 01:25:43
%S 0,1,2,3,4,5,6,9,10,16,25,32,45,65,133,134,152,250,1542,3190,3222,
%T 3612,3613,4183,9286,35411,37271,72865,191334,193393,376889,535069,
%U 794376,1110699,2236488,3021897,4431562,8094840,9885773,10883814,16219922
%N Base 7 perfect digital invariants (written in base 10): numbers equal to the sum of the k-th powers of their base-7 digits, for some k.
%C Whenever a(n) is a multiple of 7, then a(n+1) = a(n) + 1 is also a base 7 perfect digital invariant, with the same exponent k. - _M. F. Hasler, Nov 21 2019_
%H Joseph Myers, <a href="/A162228/b162228.txt">Table of n, a(n) for n=1..868</a> (complete to 200 base 7 digits)
%o (PARI) select( {is_A162228(n, b=7)=n<b||forstep(k=logint(n,max(vecmax(b=digits(n, b)), 2)), 2, -1, my(s=vecsum([d^k|d<-b])); s>n||return(s==n))}, [0..10^5]) \\ _M. F. Hasler_, Nov 21 2019
%Y Cf. A162229 (corresponding exponents), A010350 (restriction to power = number of digits), A033839, A162230. In other bases: A162216 (base 3), A162219 (base 4), A162222 (base 5), A162225 (base 6), A162231 (base 8), A162234 (base 9), A023052 (base 10).
%K base,nonn
%O 1,3
%A _Joseph Myers_, Jun 28 2009
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