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!)
A070689 Numbers n such that n+1 and n^2+1 are primes. 14
1, 2, 4, 6, 10, 16, 36, 40, 66, 126, 130, 150, 156, 180, 210, 240, 250, 256, 270, 280, 306, 396, 400, 420, 430, 466, 490, 556, 570, 576, 646, 690, 700, 750, 760, 826, 906, 910, 936, 946, 966, 1060, 1096, 1150, 1276, 1290, 1306, 1320, 1366, 1566, 1570 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For any n > 1 in this sequence, (n+1)*(n^2+1) has the same nonzero digits as its prime factors in base n. - Ely Golden, Dec 12 2016

LINKS

Zak Seidov, Table of n, a(n) for n = 1..1000

MATHEMATICA

Select[ Range[2000], PrimeQ[ # + 1] && PrimeQ[ #^2 + 1] & ]

PROG

(PARI) list(lim)=my(v=List()); forprime(p=2, lim+1, if(isprime(1+(p-1)^2), listput(v, p-1))); Vec(v) \\ Charles R Greathouse IV, Dec 13 2016

CROSSREFS

Cf. A067720.

Sequence in context: A164142 A048833 A204656 * A091611 A107742 A228779

Adjacent sequences:  A070686 A070687 A070688 * A070690 A070691 A070692

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, May 13 2002

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 July 7 15:49 EDT 2020. Contains 335495 sequences. (Running on oeis4.)