Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #4 Feb 09 2020 20:11:20
%S 30514,36777,43978,3474262,5745125,10628554,16567494,40831527,
%T 58008301,111798477,142981839,288834504,392413941,580867202,650141557,
%U 944224497,967593411,1874210882,6306287377,6442064745,7377567197,8121464245
%N Numbers k such that k and k + 1 have the same norm of the sum of divisors in Gaussian integers.
%C The first term, 30514, is also a number k such that k and k + 1 have the sum divisors in Gaussian integers: -54720 + 48960*i (where i is the imaginary unit). What is the next term with this property?
%C No more terms below 1.5*10^10.
%e 30514 is a term since A103230(30514) = A103230(30515) = 5391360000.
%t csigma[n_] :=(Abs @ DivisorSigma[1, n, GaussianIntegers -> True])^2; seq = {}; n1 = csigma[1]; Do[n2 = csigma[n]; If[n1 == n2, AppendTo[seq, n - 1]]; n1 = n2, {n, 2, 5*10^5}]; seq
%Y Cf. A002961, A064125, A103228, A103229, A103230, A293183, A306985.
%K nonn,more
%O 1,1
%A _Amiram Eldar_, Feb 09 2020