cp's OEIS Frontend

A349487 a(n) = A132739((n-5)*(n+5)).

%I A349487 #26 Dec 05 2021 18:47:43
%S A349487 11,24,39,56,3,96,119,144,171,8,231,264,299,336,3,416,459,504,551,24,
%T A349487 651,704,759,816,7,936,999,1064,1131,48,1271,1344,1419,1496,63,1656,
%U A349487 1739,1824,1911,16,2091,2184,2279,2376,99,2576,2679,2784,2891,24,3111
%N A349487 a(n) = A132739((n-5)*(n+5)).
%C A349487 Shares 614 initial terms with A061043. First difference is A061043(620)=615 vs. a(620)=123.
%F A349487 a(n) = A132739(A098603(n-5)).
%e A349487 a(9)  = A132739(( 9-5)*( 9+5)) = A132739(56) = 56,
%e A349487 a(10) = A132739((10-5)*(10+5)) = A132739(75) = 3,
%e A349487 a(11) = A132739((11-5)*(11+5)) = A132739(96) = 96.
%t A349487 Table[Last@Select[Divisors[(n - 5)*(n + 5)], Mod[#, 5] != 0 &], {n, 6,
%t A349487    56}] (* _Giorgos Kalogeropoulos_, Nov 19 2021 *)
%t A349487 Table[(n - 5)*(n + 5)/5^IntegerExponent[(n - 5)*(n + 5), 5], {n, 6, 56}] (* _Amiram Eldar_, Nov 22 2021 *)
%o A349487 (PARI) A132739(n)=n/5^valuation(n, 5);
%o A349487 a(n) = A132739((n-5)*(n+5));
%o A349487 [a(n)|n<-[6..25]]
%o A349487 (Ruby) p (6..25).map { |n| x = (n-5)*(n+5); x /= 5 while (x % 5) == 0; x }
%o A349487 (Python)
%o A349487 def A349487(n):
%o A349487     a, b = divmod(n*n-25, 5)
%o A349487     while b == 0:
%o A349487         a, b = divmod(a,5)
%o A349487     return 5*a+b # _Chai Wah Wu_, Dec 05 2021
%Y A349487 Cf. A061043, A098603, A132739.
%K A349487 nonn
%O A349487 6,1
%A A349487 _Simon Strandgaard_, Nov 19 2021