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A225136 Numbers that are concatenations of triprimes.

%I A225136 #13 May 06 2013 11:28:01
%S A225136 88,128,188,208,278,288,308,428,448,458,508,528,638,668,688,708,758,
%T A225136 768,788,808,812,818,820,827,828,830,842,844,845,850,852,863,866,868,
%U A225136 870,875,876,878,888,892,898,899,928,988,998,1028,1058,1108,1148,1168,1178
%N A225136 Numbers that are concatenations of triprimes.
%H A225136 Christian N. K. Anderson, <a href="/A225136/b225136.txt">Table of n, a(n) for n = 1..10000</a>
%H A225136 Christian N. K. Anderson, <a href="/A225136/a225136.txt">Table of n, a(n), all possible separations of a(n) into triprimes</a> for n=1..10000.
%e A225136 88 = 8|8, both of which are triprime because 8=2*2*2.
%e A225136 458 = 45 | 8 = 3*3*5 | 2*2*2.
%e A225136 12428 can be split into triprimes in three ways: 12|428, 12|42|8, and 124|28.
%o A225136 (R) library(gmp); istriprime=function(x) ifelse(x<8,F,length(factorize(x))==3)
%o A225136 splithasproperty<-function(n,FUN,curdig=1,res=list(),curspl=c()) {
%o A225136 no0<-function(s){ while(substr(s,1,1)=="0" & nchar(s)>1) s=substr(s,2,nchar(s)); s}
%o A225136     s=as.character(n)
%o A225136     if(curdig>nchar(s)) return(res)
%o A225136     if(length(curspl)>0) if(FUN(as.bigz(no0(substr(s,curdig,nchar(s)))))) res[[length(res)+1]]=curspl
%o A225136     for(i in curdig:nchar(s))
%o A225136         if(FUN(as.bigz(no0(substr(s,curdig,i)))))
%o A225136             res=splithasproperty(n,FUN,i+1,res,c(curspl,i))
%o A225136     res
%o A225136 }
%o A225136 which(sapply(1:500,function(x) length(splithasproperty(x,istriprime)))>0)
%Y A225136 Cf. A106582, A019549, A030459.
%K A225136 nonn,base,less
%O A225136 1,1
%A A225136 _Kevin L. Schwartz_ and _Christian N. K. Anderson_, Apr 29 2013