A145989 Run lengths of consecutive primes == 1 (mod 4) where the run length is at least 2.

2, 2, 3, 2, 2, 2, 2, 2, 2, 4, 3, 2, 2, 3, 2, 4, 2, 2, 2, 3, 3, 2, 2, 4, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 2, 2, 2, 2, 5, 2, 3, 2, 2, 2, 2, 2

Offset

1,1

Comments

The run lengths of 1's in A039702 are 1, 2, 1, 2, 1, 1, 1, 3,.. as listed in A091318. Deleting all 1's from A091318 generates this sequence here. - R. J. mathar, Sep 30 2011

References

Enoch Haga, Exploring Primes on Your PC and the Internet, 1994-2007. Pp. 30-31. ISBN 978-1-885794-24-6

Links

Table of n, a(n) for n=1..60.

Example

a(1)=2 because this sequence includes consecutive runs of any length and this first occurrence > 1 is a run of 2.

Prog

(UBASIC)
10 'cluster primes
20 C=1
30 input "end #"; L
40 for N=3 to L step 2
50 S=int(sqrt(N))
60 for A=3 to S step 2
70 B=N/A
80 if int(B)*A=N then cancel for:goto 170
90 next A
100 C=C+1
110 E=N/4:E=int(E):R=N-(4*E)
120 if R=1 then print N; :C1=C1+1:T1=T1+1:print T1
130 if R=3 then T1=0
140 if R=3 then print " "; N; :C3=C3+1:T2=T2+1:print T2
150 if R=1 then T2=0
160 if T1>10 or T2>10 then stop
170 next
180 print "Total primes="; C; :print "Type A"; C1; "Type B"; C3

Crossrefs

Cf. A055623, A054624, A145986, A145988 - A145994.

Sequence in context: A031284 A064569 A370372 * A117183 A352503 A071187

Adjacent sequences: A145986 A145987 A145988 * A145990 A145991 A145992

Keyword

easy,nonn

Author

Enoch Haga, Oct 26 2008

Status

approved