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%I #15 Jan 14 2021 21:14:21
%S 0,0,0,0,0,0,0,0,0,0,0,2,4,6,8,10,12,14,16,18,0,4,8,12,16,20,24,28,32,
%T 36,0,6,12,18,24,30,36,42,48,54,0,8,16,24,32,40,48,56,64,72,0,10,20,
%U 30,40,50,60,70,80,90,0,12,24,36,48,60,72,84,96,108,0,14,28,42,56,70,84
%N a(n) = (sum of digits of n)^2 - (sum of digits^2 of n).
%C a(n) = 0 iff n is a single-digit number or is a power of ten times a single-digit number. - _Robert G. Wilson v_, May 04 2002
%F From _R. J. Mathar_, Jun 23 2009: (Start)
%F a(n) = 2*A035930(n), n <= 100.
%F a(n) = A118881(n) - A003132(n). (End)
%e n=14: sum of digits = 5, squaring gives 25; sum of squared digits of n = 1^2 + 4^2 = 17, so a(14) = 25 - 17 = 8.
%p A007953 := proc(n) add(d, d=convert(n,base,10)) ; end proc: A003132:= proc(n) add(d^2, d=convert(n,base,10)) ; end proc: A118881 := proc(n) (A007953(n))^2 ; end proc: A069816 := proc(n) A118881(n)-A003132(n) ; end proc: seq(A069816(n),n=0..80) ; # _R. J. Mathar_, Jun 23 2009
%t f[n_] := Plus @@ IntegerDigits[n]^2 - Plus @@ (IntegerDigits[n]^2); Table[ f[n], {n, 0, 100}]
%Y Cf. A067552.
%K nonn,base,easy
%O 0,12
%A _N. J. A. Sloane_, May 03 2002
%E Extended by _Robert G. Wilson v_, May 04 2002
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