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
Examples
a(1)=422 since 4=2*2 and 4 is the first composite integer.
Links
- Jens Kruse Andersen, Table of n, a(n) for n = 1..10000
Programs
-
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 *)