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A305674 Indices i such that A305671(i) != A305671(i-1). 4
2, 8, 15, 35, 55, 88, 108, 162, 195, 225, 256, 363, 370, 386, 419, 427, 437, 508, 782, 998, 1616, 1633, 1857, 1901, 3055, 3091, 4806, 4816, 5851, 5905, 6142, 6179, 6275, 6297, 6487, 6674, 7161, 7221, 7278, 7293, 7591, 7715, 13041, 13100, 13122, 13130, 13179 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
MATHEMATICA
Block[{c = Select[Range[10^4], CompositeQ], s}, s = DivisorSigma[1, c]; 1 + Position[Partition[#, 2, 1], _?(UnsameQ @@ # &)][[All, 1]] &@ Array[If[Length@ # == 1, #[[1, 1]], 0] &@ Last@ SplitBy[SortBy[Tally@ Take[s, #], Last], Last] &, Length@ s]] (* Michael De Vlieger, Jul 22 2018 *)
PROG
(PARI) composite(n) = my(i=0); forcomposite(c=1, , i++; if(i==n, return(c)))
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]))
a305671(n) = my(v=[]); for(k=1, n, v=concat(v, sigma(composite(k)))); mcv(v)
terms(n) = my(i=0); for(x=2, oo, if(a305671(x)!=a305671(x-1), print1(x, ", "); i++); if(i==n, break))
terms(11) \\ Print initial 11 terms of the sequence
CROSSREFS
Sequence in context: A297734 A100596 A295937 * A082638 A077388 A301986
KEYWORD
nonn
AUTHOR
Felix Fröhlich, Jun 08 2018
STATUS
approved

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Last modified March 28 10:31 EDT 2024. Contains 371240 sequences. (Running on oeis4.)