A255412 - OEIS

%I #11 Apr 14 2015 10:26:47

%S 4800,28800,57600,67200,86400,96000,115200,148800,144000,142800,

%T 153600,182400,201600,211200,230400,259200,345600,288000,297600,

%U 403200,326400,345600,355200,384000,403200,518400,432000,576000,470400,489600,499200,518400,528000,547200,691200,638400,748800,614400,633600,662400,672000,806400,864000,856800,720000

%N a(n) = A000203(A255334(n)).

%C Sequence gives value of sigma(n) for numbers n for which there exists k > n such that A000203(k) = A000203(n) and A007947(k) = A007947(n), where A000203 gives the sum of divisors, and A007947 gives the squarefree kernel of n. The sequence is ordered by the magnitude of n, and contains duplicates, because there are cases of multiple such pairs having the same value of sigma.

%C The first such duplicate values occur as a(17) = a(22) = 345600 and a(20) = a(25) = 403200.

%H Antti Karttunen, <a href="/A255412/b255412.txt">Table of n, a(n) for n = 1..6589</a>

%F a(n) = A000203(A255334(n)).

%F a(n) = A000203(A255423(n)).

%o (Scheme) (define (A255412 n) (A000203 (A255334 n)))

%Y Cf. A254035 (same sequence sorted into ascending order, with duplicates removed).

%Y Cf. A000203, A007947, A255334, A255423, A255424.

%K nonn

%O 1,1

%A _Antti Karttunen_, Apr 05 2015