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A145989
Run lengths of consecutive primes == 1 (mod 4) where the run length is at least 2.
4
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
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
KEYWORD
easy,nonn
AUTHOR
Enoch Haga, Oct 26 2008
STATUS
approved