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A211005
Pair (i, j) where i = number of adjacent nonprimes and j = number of adjacent primes.
4
1, 2, 1, 1, 1, 1, 3, 1, 1, 1, 3, 1, 1, 1, 3, 1, 5, 1, 1, 1, 5, 1, 3, 1, 1, 1, 3, 1, 5, 1, 5, 1, 1, 1, 5, 1, 3, 1, 1, 1, 5, 1, 3, 1, 5, 1, 7, 1, 3, 1, 1, 1, 3, 1, 1, 1, 3, 1, 13, 1, 3, 1, 5, 1, 1, 1, 9, 1, 1, 1, 5, 1, 5, 1, 3, 1, 5, 1, 5, 1, 1, 1, 9, 1, 1, 1
OFFSET
1,2
COMMENTS
Also number of consecutive occurrences of n-1 in A069754. - Reinhard Zumkeller, Dec 04 2012
Run lengths of A010051. - Paolo Xausa, Jan 17 2023
LINKS
FORMULA
a(n) = A162154(n-1), n >= 2.
EXAMPLE
----------------------------------------------------------
. Array from Number of Number of
n A000027 nonprimes primes a(n)
----------------------------------------------------------
1 1; 1 0 1
2 2, 3; 0 2 2
3 4; 1 0 1
4 5; 0 1 1
5 6; 1 0 1
6 7; 0 1 1
7 8, 9, 10; 3 0 3
8 11; 0 1 1
9 12; 1 0 1
10 13; 0 1 1
11 14, 15, 16; 3 0 3
12 17; 0 1 1
13 18; 1 0 1
14 19; 0 1 1
15 20, 21, 22; 3 0 3
16 23; 0 1 1
17 24, 25, 26, 27, 28; 5 0 5
18 29; 0 1 1
19 30; 1 0 1
20 31; 0 1 1
MATHEMATICA
A211005[upto_]:=Map[Length, Most[Split[PrimeQ[Range[upto]]]]];
A211005[500] (* Paolo Xausa, Jan 17 2023 *)
PROG
(Haskell)
import Data.List (group)
a211005 n = a211005_list !! (n-1)
a211005_list = map length $ group a069754_list
-- Reinhard Zumkeller, Dec 04 2012
CROSSREFS
1 together with A162154.
Sequence in context: A063669 A306489 A319734 * A162154 A134505 A329376
KEYWORD
nonn
AUTHOR
Omar E. Pol, Aug 11 2012
STATUS
approved