|
%I #7 Aug 26 2021 07:03:57
%S 8,26,53,98,107,143,161,170,179,188,224,233,242,260,269,278,287,296,
%T 350,368,386,404,413,431,449,476,494,503,539,548,557,584,593,629,638,
%U 647,674,683,737,746,773,791,818,827,863,872,908,926,944,998,1007,1043
%N Numbers k with digit_sum(k*k) - 1 = digit_sum((k+1)*(k+1)).
%C A240752(a(n)) = 0.
%H Reinhard Zumkeller, <a href="/A240754/b240754.txt">Table of n, a(n) for n = 1..10000</a>
%o (Haskell)
%o import Data.List (elemIndices)
%o a240754 n = a240754_list !! (n-1)
%o a240754_list = elemIndices (-1) a240752_list
%o (Python)
%o def ds(n): return sum(map(int, str(n)))
%o def ok(n): return ds(n*n) - 1 == ds((n+1)*(n+1))
%o print(list(filter(ok, range(1044)))) # _Michael S. Branicky_, Aug 26 2021
%Y Cf. A202089, A239878, A004159, A007953, A000290.
%K nonn,base
%O 1,1
%A _Reinhard Zumkeller_, Apr 12 2014
|
