cp's OEIS Frontend

A175487 a(n) = smallest prime > a(n-1) such that (a(n-1)+a(n)) is a multiple of nextprime(a(n-1)).

%I A175487 #6 Oct 13 2024 07:05:34
%S A175487 2,7,37,127,397,3613,18089,162881,1791787,41211197,370900973,
%T A175487 4821712733,43395414737,477349562419,4296146062051,227695741289567,
%U A175487 9335525392876531,326743388750679161,16663912826284638251,583236948919962339073,9915028131639359764313
%N A175487 a(n) = smallest prime > a(n-1) such that (a(n-1)+a(n)) is a multiple of nextprime(a(n-1)).
%C A175487 Next 8 terms: 406516153397213750338933,24797485357230038770679749,
%C A175487 223177368215070348936118621,5579434205376758723402966617,
%C A175487 295710012884968212340357231241,23361091017912488774888221274279,
%C A175487 1518470916164311770367734382831699,56183423898079535503606172164775599.
%e A175487 a(1)=2; a(2)=7 because 2+7=9 is a multiple of 3=nextprime(2)
%e A175487 a(3)=37 because 7+37=44 is a multiple of 11=nextprime(7)
%e A175487 37+127=164=4*41 (41=nextprime(37))
%e A175487 127+397=524=4*131 (131=nextprime(127))
%e A175487 397+3613=4010=10*401 (401=nextprime(397))
%e A175487 3613+18089=21702=6*3617 (3617=nextprime(3613))
%e A175487 18089+162881=180970=10*18097 (18097=nextprime(18089))
%e A175487 162881+1791787=1954668=12*162889 (162889=nextprime(162881))
%e A175487 1791787+41211197=43002984=24*1791791 (1791791=nextprime(1791787)).
%t A175487 <<NumberTheory`NumberTheoryFunctions`; a=2;np=NextPrime[a];s={a};
%t A175487 Do[Do[If[PrimeQ[p=np*k-a],AppendTo[s,p];a=p;np=NextPrime[a];Break[]],{k,1000}],{30}];s
%Y A175487 Cf. A178468.
%K A175487 nonn
%O A175487 1,1
%A A175487 _Zak Seidov_, May 28 2010