

A082073


First difference set of primes with 4k+1 form: A002144.


10



8, 4, 12, 8, 4, 12, 8, 12, 16, 8, 4, 8, 4, 24, 12, 8, 16, 8, 12, 4, 32, 4, 8, 16, 12, 8, 4, 12, 20, 4, 20, 12, 4, 20, 16, 8, 4, 8, 12, 12, 16, 8, 4, 48, 12, 20, 16, 12, 8, 16, 8, 12, 4, 24, 12, 8, 12, 4, 24, 8, 24, 24, 4, 8, 4, 24, 12, 12, 8, 24, 4, 20, 4, 48, 8, 4, 12, 24, 20, 12, 4, 8, 12
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OFFSET

1,1


LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000


FORMULA

a(n) = A002144(n+1)  A002144(n).


EXAMPLE

first and second 4k+1 primes are 5 and 13, so a(1)=135=8;
a(n) is divisible by 4.


MATHEMATICA

k=0; m=4; r=1; Do[s=Mod[Prime[n], m]; If[Equal[s, r], rp=ep; k=k+1; ep=Prime[n]; Print[(eprp)]; ], {n, 1, 1000}]


PROG

(PARI) p=5; forprime(q=7, 1e3, if(q%4==1, print1(qp", "); p=q)) \\ Charles R Greathouse IV, May 13 2012


CROSSREFS

Cf. A002144, A002145, A082074A082076.
Sequence in context: A194184 A194217 A239971 * A244209 A156279 A203072
Adjacent sequences: A082070 A082071 A082072 * A082074 A082075 A082076


KEYWORD

nonn,easy


AUTHOR

Labos Elemer, Apr 07 2003


STATUS

approved



