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%I #15 Aug 04 2018 14:44:55
%S 2,15,55,108,195,256,370,419,437,782,1616,1857,3055,4806,5851,6142,
%T 6275,6487,7161,7278,7591,13041,13122,13179,14904,14979,15451,21767,
%U 32056,39478,79649,148518,174716,273952,400581
%N Indices i where a run of zeros starts in A305671.
%C Numbers i such that A305671(i) = 0 and A305671(i-1) != 0.
%t Block[{c = Select[Range[10^3], CompositeQ], s}, s = DivisorSigma[1, c]; Select[SplitBy[Partition[Position[Array[If[Length@ # == 1, #[[1, 1]], 0] &@ Last@ SplitBy[SortBy[Tally@ Take[s, #], Last], Last] &, Length@ s], 0][[All, 1]], 2, 1], Differences], Length@ # > 1 &][[All, 1, 1]]] (* _Michael De Vlieger_, Jun 14 2018 *)
%o (PARI) mcv(v) = my(w=vecsort(v, , 8), count=vector(#w), ind=0, i=0); for(x=1, #w, for(y=1, #v, if(w[x]==v[y], count[x]++))); for(k=1, #count, if(count[k]==vecmax(count), ind=k; i++)); if(i > 1, return(0), return(w[ind]))
%o my(v=[], i=1, t=0); forcomposite(c=1, , v=concat(v, [sigma(c)]); if(mcv(v)==0, if(t==0, print1(i, ", ")); t++, t=0); i++)
%Y Cf. A305671, A305672, A305674, A305675, A305676.
%K nonn,more
%O 1,1
%A _Felix Fröhlich_, Jun 08 2018
%E More terms from _Michael De Vlieger_, Jun 14 2018
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