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

1,1

Comments

This is to A225873 as cubes A000578 are to squares A000290.

Links

Christian N. K. Anderson, Table of n, a(n) for n = 1..10000

Example

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.

Prog

(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") }
(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

Crossrefs

Cf. A000578, A225873.

Sequence in context: A030673 A030683 A038840 * A032599 A016839 A128831

Adjacent sequences: A226087 A226088 A226089 * A226091 A226092 A226093

Keyword

nonn,easy,base

Author

Jonathan Vos Post, May 25 2013

Status

approved