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A226090 Cubes that become prime when their most significant (or leftmost) digit is removed. 5
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified May 22 14:32 EDT 2019. Contains 323480 sequences. (Running on oeis4.)