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 A225136 Numbers that are concatenations of triprimes. 1
 88, 128, 188, 208, 278, 288, 308, 428, 448, 458, 508, 528, 638, 668, 688, 708, 758, 768, 788, 808, 812, 818, 820, 827, 828, 830, 842, 844, 845, 850, 852, 863, 866, 868, 870, 875, 876, 878, 888, 892, 898, 899, 928, 988, 998, 1028, 1058, 1108, 1148, 1168, 1178 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Christian N. K. Anderson, Table of n, a(n) for n = 1..10000 Christian N. K. Anderson, Table of n, a(n), all possible separations of a(n) into triprimes for n=1..10000. EXAMPLE 88 = 8|8, both of which are triprime because 8=2*2*2. 458 = 45 | 8 = 3*3*5 | 2*2*2. 12428 can be split into triprimes in three ways: 12|428, 12|42|8, and 124|28. PROG (R) library(gmp); istriprime=function(x) ifelse(x<8, F, length(factorize(x))==3) splithasproperty<-function(n, FUN, curdig=1, res=list(), curspl=c()) { no0<-function(s){ while(substr(s, 1, 1)=="0" & nchar(s)>1) s=substr(s, 2, nchar(s)); s} s=as.character(n) if(curdig>nchar(s)) return(res) if(length(curspl)>0) if(FUN(as.bigz(no0(substr(s, curdig, nchar(s)))))) res[[length(res)+1]]=curspl for(i in curdig:nchar(s)) if(FUN(as.bigz(no0(substr(s, curdig, i))))) res=splithasproperty(n, FUN, i+1, res, c(curspl, i)) res } which(sapply(1:500, function(x) length(splithasproperty(x, istriprime)))>0) CROSSREFS Cf. A106582, A019549, A030459. Sequence in context: A196581 A179245 A174651 * A039445 A300144 A247528 Adjacent sequences: A225133 A225134 A225135 * A225137 A225138 A225139 KEYWORD nonn,base,less AUTHOR Kevin L. Schwartz and Christian N. K. Anderson, Apr 29 2013 STATUS approved

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Last modified September 29 02:45 EDT 2023. Contains 365749 sequences. (Running on oeis4.)