A305672 Indices i where a run of nonzero values starts in A305671.

1, 8, 35, 88, 162, 225, 363, 386, 427, 508, 998, 1633, 1901, 3091, 4816, 5905, 6179, 6297, 6674, 7221, 7293, 7715, 13100, 13130, 13238, 14927, 15012, 15520, 22413, 32219, 39561, 79864, 148622, 175500, 274750, 402174

Offset: 1

Author

Felix Fröhlich, Jun 08 2018

Keywords

• nonn
• more

Comments

For n > 1, numbers i such that A305671(i) != 0 and A305671(i-1) = 0.

Crossrefs

Cf. A305671, A305673, A305674, A305675, A305676.

Programs

Mathematica

Block[{c = Select[Range[10^4], CompositeQ], s}, s = DivisorSigma[1, c]; Prepend[1 + Accumulate[Total /@ #], #[[1, 1]]] &@ Partition[Length /@ SplitBy[#, # == 0 &], 2, 2] &@ Array[If[Length@ # == 1, #[[1, 1]], 0] &@ Last@ SplitBy[SortBy[Tally@ Take[s, #], Last], Last] &, Length@ s]] (* Michael De Vlieger, Jul 21 2018 *)

PARI

my(v=[], i=0, b=0, idx=1); forcomposite(c=1, , my(sig=sigma(c)); if(#v < sig, v=concat(v, vector(sig-#v))); v[sig]++; for(k=1, #v, if(v[k]==vecmax(v), i++)); if(i < 2, if(b==0, print1(idx, ", "); b=1)); if(i > 1, b=0); idx++; i=0)