A226090 Cubes that become prime when their most significant (or leftmost) digit is removed.
27, 343, 729, 1331, 2197, 6859, 29791, 50653, 59319, 103823, 185193, 226981, 250047, 389017, 456533, 704969, 804357, 2048383, 2352637, 3869893, 5000211, 5929741, 9393931, 11697083, 13312053, 13651919, 14348907, 15813251, 19034163, 20346417, 24642171, 27818127
Offset: 1
Examples
a(1) = 27 because removing the leftmost digit gives 7, a prime. a(8) = 50653 because removing the leftmost digit gives 0653 = 653, which is prime. a(21) = 5000211 because removing the leftmost digit gives 000211 = 00211 = 0211 = 211, which is prime.
Links
- Christian N. K. Anderson, Table of n, a(n) for n = 1..10000
Programs
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PARI
for(n=3,1e3,t=Vec(Str(n^3));if(isprime(eval(concat(t[2..#t]))),print1(n^3", "))) \\ Charles R Greathouse IV, Jun 10 2013
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R
library(gmp); no0<-function(s){ while(substr(s,1,1)=="0" & nchar(s)>1) s=substr(s,2,nchar(s)); s}; trimL=function(x) { x=as.character(x); ifelse(nchar(x)<2,0,no0(substr(x,2,nchar(x)))) }; y=as.bigz(rep(0,10000)); len=0; n=as.bigz(-1); while(len<10000) if(isprime(trimL((n=n+1)^3))) {y[(len=len+1)]=n^3; if(len%%100==0) cat(len,as.character(y[len]),"\n") }
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