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

 

Logo

Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A071635 Number of decompositions of 4*n+2 into sum of two primes of form 4*k+1. 3
0, 0, 1, 0, 1, 1, 1, 1, 2, 0, 2, 2, 1, 2, 3, 0, 3, 2, 2, 3, 2, 1, 3, 2, 1, 4, 3, 2, 5, 3, 2, 5, 3, 2, 3, 4, 2, 5, 4, 1, 5, 3, 3, 4, 4, 1, 6, 4, 3, 6, 5, 2, 9, 3, 3, 4, 4, 2, 6, 4, 2, 8, 4, 4, 5, 4, 3, 8, 5, 2, 7, 7, 4, 9, 6, 3, 7, 6, 3, 6, 6, 2, 12, 5, 4, 8, 6, 5, 10, 4, 2, 10, 7, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,9

LINKS

Andrew Howroyd, Table of n, a(n) for n = 0..10000

Index entries for sequences related to Goldbach conjecture.

FORMULA

a(n) = A002375(2*n+1) - A156642(n). - Vladimir Shevelev, Feb 12 2009

EXAMPLE

a(10)=2 as 4*10+2=42=5+37=(4*1+1)+(4*9+1)=13+29=(4*3+1)+(4*7+1) and the other two decompositions 42=11+31=(4*2+3)+(4*7+3)=19+23=(4*4+3)+(4*5+3), A002375(21)=4;

for a(m)=0 see A071636.

PROG

(PARI) a(n)={my(s=0); forprime(p=3, 2*n+1, if(p%4==1 && isprime(4*n+2-p), s++)); s} \\ Andrew Howroyd, Feb 02 2020

CROSSREFS

Cf. A002375, A002144, A156642.

Sequence in context: A060964 A118206 A029314 * A156643 A308626 A268755

Adjacent sequences:  A071632 A071633 A071634 * A071636 A071637 A071638

KEYWORD

nonn,look

AUTHOR

Reinhard Zumkeller, May 27 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 December 4 15:46 EST 2020. Contains 338928 sequences. (Running on oeis4.)