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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

Table of n, a(n) for n=1..36.

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

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

Sequence in context: A214725 A136016 A257454 * A100907 A303383 A265840

Adjacent sequences:  A305669 A305670 A305671 * A305673 A305674 A305675

KEYWORD

nonn,more

AUTHOR

Felix Fröhlich, Jun 08 2018

STATUS

approved

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Last modified November 15 06:11 EST 2019. Contains 329144 sequences. (Running on oeis4.)