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A087032
a(n) = 1 if 2*A151800(n) - n is prime, otherwise 0, where A151800(n) is the smallest prime > n.
2
1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0
OFFSET
1,1
COMMENTS
There is no subsequence of two ones; number of zeros in each group is odd, see A087033.
FORMULA
a(n) = 1 if A087030(n) is prime, 0 if it is composite.
a(n) = A010051((2*A151800(n))-n). - Antti Karttunen, Oct 09 2018
EXAMPLE
a(1)=1 because the smallest prime > 1 is 2 and 2*2-1=3 is prime.
MATHEMATICA
bb={}; Do[bb={bb, If[PrimeQ[2(Prime[PrimePi[n]+1])-n], 1, 0]}, {n, 1000}]; Flatten[bb]
PROG
(PARI) A087032(n) = isprime((2*nextprime(1+n))-n); \\ Antti Karttunen, Oct 09 2018
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Zak Seidov, Jul 31 2003
EXTENSIONS
Definition edited by Antti Karttunen, Oct 09 2018
STATUS
approved