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A323162 a(n) = 1 if both n and n-1 are composite, 0 otherwise. 4
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET
1
COMMENTS
Characteristic function of A005381.
LINKS
FORMULA
a(1) = 0; for n > 1, a(n) = (1-A010051(n-1)) * (1-A010051(n)).
a(A005381(n)) = 1, a(A093515(n)) = 0.
For n >= 4, a(n) = 1-A090405(n-2).
MATHEMATICA
Map[Boole[AllTrue[#, CompositeQ]] &, Partition[Range[0, 120], 2, 1]] (* Michael De Vlieger, Jan 07 2019 *)
PROG
(PARI) A323162(n) = ((n>1)&&(!isprime(n))&&(!isprime(n-1)));
CROSSREFS
Sequence in context: A011722 A276404 A277153 * A185017 A359472 A295883
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jan 07 2019
STATUS
approved

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Last modified March 29 03:51 EDT 2024. Contains 371264 sequences. (Running on oeis4.)