A091318 Lengths of runs of 1's in A039702.

1, 2, 1, 2, 1, 1, 1, 3, 2, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 4, 1, 1, 3, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 3, 2, 1, 4, 2, 1, 1, 2, 2, 3, 1, 1, 3, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 4, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 2, 2, 2, 1, 2, 3, 2, 2, 1, 1, 2, 1, 2, 2, 1, 2, 1, 2, 1, 1, 1, 2, 1, 2, 2, 2, 3, 3, 3

Offset

1,2

Comments

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

Example

a(8)=3 because this is the sequence of primes congruent to 1 mod 4: 89, 97, 101. The next prime is 103, a prime 3 mod 4.

Mathematica

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

Crossrefs

Cf. A002144, A002145, A039702, A091267, A091237.

Sequence in context: A175024 A175023 A128115 * A198898 A003639 A174110

Adjacent sequences: A091315 A091316 A091317 * A091319 A091320 A091321

Keyword

easy,nonn

Author

Enoch Haga, Feb 22 2004

Status

approved