The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A351925 Squares which are the concatenation of two primes. 1
 25, 289, 361, 529, 729, 2401, 2601, 2809, 4761, 5329, 5929, 7569, 11449, 11881, 15129, 19881, 21609, 22801, 23409, 24649, 25281, 26569, 29241, 29929, 31329, 34969, 36481, 39601, 47961, 52441, 53361, 54289, 57121, 58081, 59049, 71289, 77841, 83521, 89401 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The first term that is the concatenation of two primes in more than one way is a(11) = 5929 = 5 | 929 = 59 | 29. - Robert Israel, Oct 01 2023 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 FORMULA Intersection of A106582 and A000290. EXAMPLE 25 is the concatenation of 2 and 5, both primes. 4761 is the concatenation of 47 and 61, both primes. MAPLE L:= NULL: count:=0: for x from 1 by 2 while count < 100 do xs:= x^2; for i from 1 to ilog10(xs) do a:= xs mod 10^i; if a > 10^(i-1) and isprime(a) then b:= (xs-a)/10^i; if isprime(b) then L:= L, xs; count:= count+1; break fi fi od od: L; # Robert Israel, Oct 01 2023 PROG (PARI) isb(n)={my(d=10); while(d

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 23 20:17 EDT 2024. Contains 373653 sequences. (Running on oeis4.)