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Sum of squares of digits of prime factors of n, with multiplicity.
0

%I #15 Jun 08 2024 15:41:10

%S 0,4,9,8,25,13,49,12,18,29,2,17,10,53,34,16,50,22,82,33,58,6,13,21,50,

%T 14,27,57,85,38,10,20,11,54,74,26,58,86,19,37,17,62,25,10,43,17,65,25,

%U 98,54,59,18,34,31,27,61,91,89,106,42

%N Sum of squares of digits of prime factors of n, with multiplicity.

%C Differs from A067666 if any prime factor exceeds 1 digit. Fixed points include 16, 27. See also: A067666 Sum of squares of prime factors of n (counted with multiplicity). See also: A003132 Sum of squares of digits of n. See also: A118503 Sum of digits of prime factors of n, with multiplicity.

%F a(n) = SUM[i=1..k] (e_i)*A003132(p_i) where prime decomposition of n = (p_1)^(e_1) * (p_2)^(e_2) * ... * (p_k)^(e_k).

%e a(22) = 6 because 22 = 2 * 11 and the sum of squares of digits of prime factors is 2^2 + 1^2 + 1^2.

%e a(121) = 4 because 121 = 11^2 = 11 * 11, so 1^2 + 1^2 + 1^2 + 1^2 = 4.

%t Join[{0},Table[Total[Flatten[IntegerDigits/@(Flatten[Table[#[[1]],#[[2]]]&/@ FactorInteger[ n]])]^2],{n,2,60}]] (* _Harvey P. Dale_, Nov 17 2022 *)

%Y Cf. A001221, A001222, A003132, A005063, A007953, A007954, A067666, A095402, A118503.

%K base,easy,nonn

%O 1,2

%A _Jonathan Vos Post_, May 07 2006

%E a(0) removed by _Andrey Zabolotskiy_, Jun 08 2024