cp's OEIS Frontend

A379982 Nonmultiples of 10 that are divisible by the square of the sum of the squares of their digits.

%I A379982 #12 Jan 11 2025 03:46:38
%S A379982 1,2023,4332,30324,31311,43011,52022,52215,71824,101376,110201,116964,
%T A379982 120213,120472,120612,131072,141312,145152,202312,230202,233928,
%U A379982 244634,298374,305252,320305,327184,409374,506056,511104,519168,565152,615627,652118,667815,680625
%N A379982 Nonmultiples of 10 that are divisible by the square of the sum of the squares of their digits.
%H A379982 Amiram Eldar, <a href="/A379982/b379982.txt">Table of n, a(n) for n = 1..10000</a>
%H A379982 Pradip Kumar Pal and Kaushik Gopalan, <a href="https://www.ripublication.com/ijome23/ijomev13n1_04.pdf">Second Order Harshad Number</a>, International Journal of Mathematical Education, Vol. 13, No. 1 (2023), pp. 25-26.
%e A379982 2023 is a term since 2023 is not divisible by 10 and it is divisible by (2^2 + 0^2 + 2^2 + 3^2)^2 = 289.
%t A379982 Select[Range[10^6], ! Divisible[#, 10] && Divisible[#, (Plus @@ (IntegerDigits[#]^2))^2] &]
%o A379982 (PARI) isok(k) = k % 10 && !(k % vecsum(apply(x -> x^2, digits(k)))^2);
%o A379982 (Python)
%o A379982 def ok(n): return n%10 and n%sum(di**2 for di in map(int, str(n)))**2 == 0
%o A379982 print([k for k in range(10**6) if ok(k)]) # _Michael S. Branicky_, Jan 10 2025
%Y A379982 Intersection of A067251 and A379980.
%K A379982 nonn,base
%O A379982 1,2
%A A379982 _Amiram Eldar_, Jan 07 2025