A091267 Lengths of runs of 3's in A039702.

1, 2, 2, 1, 2, 1, 2, 2, 2, 2, 1, 1, 2, 1, 1, 4, 1, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 2, 7, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 2, 2, 3, 1, 1, 2, 1, 2, 5, 1, 2, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 3, 1, 1, 1, 2, 3, 2, 2, 5, 5, 1, 1, 1, 2, 1, 1, 1, 1, 2, 4, 2, 1, 1, 1, 1, 2, 3, 1, 1, 1, 2, 2, 1, 1, 3, 4, 1

Offset

1,2

Comments

Number of primes congruent to 3 mod 4 in sequence before interruption by a prime 1 mod 4.

References

Enoch Haga, Exploring prime numbers on your PC and the Internet with directions to prime number sites on the Internet, 2001, pages 30-31. ISBN 1-885794-17-7.

Links

T. D. Noe, Table of n, a(n) for n = 1..10000

Formula

Count primes congruent to 3 mod 4 in sequence before interruption by a prime divided by 4 with remainder 1.

Example

a(16)=4 because this is the sequence of primes congruent to 3 mod 4: 199, 211, 223, 227. The next prime is 229, a prime 1 mod 4.

Mathematica

t = Length /@ Split[Table[Mod[Prime[n], 4], {n, 2, 400}]]; Most[Transpose[Partition[t, 2]][[1]]] (* T. D. Noe, Sep 21 2012 *)

Crossrefs

Cf. A002144, A002145, A091318, A039702, A091237.

Sequence in context: A370558 A191971 A156051 * A003643 A092788 A058062

Adjacent sequences: A091264 A091265 A091266 * A091268 A091269 A091270

Keyword

easy,nonn

Author

Enoch Haga, Feb 22 2004

Status

approved