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A091318 Lengths of runs of 1's in A039702. 7
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified August 28 03:16 EDT 2015. Contains 261112 sequences.