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 #5 Oct 12 2019 19:08:44
%S 3,5,11,29,59,179,239,419,1319,2339,3119,3359,6299,7559,21599,21839,
%T 33599,35279,42839,55439,100799,110879,287279,415799,957599,1621619,
%U 1713599,1867319,1940399,2489759,3991679,6652799,11531519,18258239,22822799,26732159,28828799
%N Lesser of twin primes p such that d(p+1) > d(q+1) for all lessers of twin primes q < p, where d(n) is the number of divisors of n (A000005).
%C The corresponding values of d(p+1) are 3, 4, 6, 8, 12, 18, 20, 24, 32, 36, 40, 48, 54, 64, 72, 80, 84, 90, 96, 120, 126, 144, 160, 192, 216, 240, 252, 256, 270, 288, 320, 384, 432, 448, 480, 512, 576, ...
%t dm = DivisorSigma[0, 4]; s = {3}; Do[If[!PrimeQ[6n - 1] || !PrimeQ[6n + 1], Continue[]]; d = DivisorSigma[0, 6n]; If[d > dm, dm = d; AppendTo[s, 6n - 1]], {n, 1, 10^5}]; s
%Y Cf. A000005, A001359, A068507, A321995, A326392.
%K nonn
%O 1,1
%A _Amiram Eldar_, Oct 12 2019