login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A153050 Six-digit squares that are concatenation of two 3-digit primes. 2
101761, 113569, 127449, 131769, 137641, 149769, 167281, 199809, 349281, 439569, 463761, 491401, 641601, 683929, 797449 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n)=(A153048(n))^2.

There are exactly 15 such numbers.

LINKS

Table of n, a(n) for n=1..15.

MATHEMATICA

c = 0; t = 1000; re = Sort[Reap[Do[If[PrimeQ[p], Do[If[PrimeQ[q], r = p*t + q; s = Sqrt[r]; If[s == Floor[s], c++; Sow[r]]], {q, 101, 999, 2}]], {p, 101, 999, 2}]][[2, 1]]]

concatpQ[n_]:=Module[{idn=IntegerDigits[n], a, b}, a=FromDigits[Take[idn, 3]]; b=FromDigits[Take[idn, -3]]; IntegerLength[a]==IntegerLength[b]==3 && PrimeQ[a]&&PrimeQ[b]]; Select[Range[316, 1000]^2, concatpQ] (* Harvey P. Dale, Mar 09 2012 *)

CROSSREFS

Cf. A153048.

Sequence in context: A023077 A077760 A218170 * A203592 A106813 A186096

Adjacent sequences:  A153047 A153048 A153049 * A153051 A153052 A153053

KEYWORD

fini,full,nonn,base

AUTHOR

Zak Seidov, Dec 17 2008

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 8 02:26 EDT 2021. Contains 343652 sequences. (Running on oeis4.)