A245315 Concatenate n-th composite number with concatenation of its prime factors in ascending order.

422, 623, 8222, 933, 1025, 12223, 1427, 1535, 162222, 18233, 20225, 2137, 22211, 242223, 2555, 26213, 27333, 28227, 30235, 3222222, 33311, 34217, 3557, 362233, 38219, 39313, 402225, 42237, 442211, 45335, 46223, 4822223

Offset

1,1

Links

Jens Kruse Andersen, Table of n, a(n) for n = 1..10000

Example

a(1)=422 since 4=2*2 and 4 is the first composite integer.

Mathematica

f[n_]:=FactorInteger[n]; con[A_]:=(v1={}; l=Length[A]; Do[v1=Join[v1, IntegerDigits[A[[k]]]], {k, l}]; FromDigits[v1]); alfa[n_]:=(b=f[n]; j=Length[b]; c=Table[Table[b[[k]][[1]], {b[[k]][[2]]}], {k, j}]; w={}; Do[w=Join[w, c[[k]]], {k, j}]; con[w]); na[n_]:=con[{n, alfa[n]}]; v=Select[Range[2, 1000], !PrimeQ[#]&]; Table[na[v[[k]]], {k, 32}]
ncpf[n_]:=FromDigits[Join[IntegerDigits[n], Flatten[IntegerDigits/@Table[ #[[1]], #[[2]]]&/@FactorInteger[n]]]]; ncpf/@Select[Range[ 100], CompositeQ] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jul 03 2019 *)

Crossrefs

Cf. A002808, A245316.

Sequence in context: A303334 A109505 A109473 * A357890 A200200 A231585

Adjacent sequences: A245312 A245313 A245314 * A245316 A245317 A245318

Keyword

nonn,base

Author

Jahangeer Kholdi, Sep 15 2014

Status

approved