A305675 Run lengths of successive equal terms in A305671.

1, 6, 7, 20, 20, 33, 20, 54, 33, 30, 31, 107, 7, 16, 33, 8, 10, 71, 274, 216, 618, 17, 224, 44, 1154, 36, 1715, 10, 1035, 54, 237, 37, 96, 22, 190, 187, 487, 60, 57, 15, 298, 124, 5326, 59, 22, 8, 49, 59, 1666, 23, 52, 33, 439, 69, 6247, 646, 9643, 163, 7259

Offset

1,2

Comments

First differences of A305672 UNION A305673.

Links

Table of n, a(n) for n=1..59.

Mathematica

Block[{c = Select[Range[10^4], CompositeQ], s}, s = DivisorSigma[1, c]; Most[Length /@ SplitBy[#, # == 0 &]] &@ 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, j=1); for(k=1, oo, if(a305671(k)==a305671(k+1), j++, if(j > 0, print1(j, ", "); i++; j=1)); if(i==n, break))
terms(20) \\ Print initial 20 terms of the sequence

Crossrefs

Cf. A305671, A305672, A305673, A305674, A305676.

Sequence in context: A285840 A285819 A287760 * A210605 A175262 A345911

Adjacent sequences: A305672 A305673 A305674 * A305676 A305677 A305678

Keyword

nonn

Author

Felix Fröhlich, Jun 08 2018

Status

approved