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A305672 Indices i where a run of nonzero values starts in A305671. 5
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
For n > 1, numbers i such that A305671(i) != 0 and A305671(i-1) = 0.
LINKS
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 *)
PROG
(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)
CROSSREFS
Sequence in context: A214725 A136016 A257454 * A100907 A303383 A265840
KEYWORD
nonn,more
AUTHOR
Felix Fröhlich, Jun 08 2018
STATUS
approved

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Last modified February 23 20:31 EST 2024. Contains 370288 sequences. (Running on oeis4.)