OFFSET
1,4
COMMENTS
Bisection of A256262.
FORMULA
EXAMPLE
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. Other Twin
. odd numbers primes
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1 1 3, 5, 7 1
2 9 11, 13 1
3 15 17, 19 1
4 21, 23, 25, 27 29, 31 4
5 33, 35, 37, 39 41, 43 4
...
For n = 5, between the successive pairs of twin primes [29, 31] and [41, 43] there are four odd numbers that are not twin primes: 33, 35, 37, 39, so a(5) = 4.
CROSSREFS
KEYWORD
nonn
AUTHOR
Omar E. Pol, Jun 15 2015
STATUS
approved