A225151 Squares which are a decimal concatenation of triprimes.

12544, 15376, 19044, 20164, 27556, 28561, 42436, 45369, 45796, 75076, 81796, 86436, 87025, 89401, 98596, 114244, 116964, 123201, 124609, 125316, 126025, 127449, 128164, 131044, 139876, 141376, 150544, 174724, 175561, 184041, 188356, 190969, 191844, 207025

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), sqrt(a(n)), all possible separations of a(n) into triprimes

Example

a(10) is 75076, which splits into 75|076. 75 = 3*5*5; 76 = 2*2*19.

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^2, istriprime)))>0)^2

Crossrefs

Cf. A014612, A030459, A030461, A000290, A019547.

Sequence in context: A252164 A045217 A298313 * A237907 A251296 A205757

Adjacent sequences: A225148 A225149 A225150 * A225152 A225153 A225154

Keyword

nonn,base

Author

Kevin L. Schwartz and Christian N. K. Anderson, Apr 30 2013

Status

approved