

A100821


a(n) = 1 if prime(n) + 2 = prime(n+1), otherwise 0.


3



0, 1, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0
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OFFSET

1,1


COMMENTS

Same as A062301 except for starting point.
a(n)=1 iff prime(n) is the smaller of a pair of twin primes, else a(n)=0. This sequence can be derived from the sequence b(n)=1 iff n and n+2 are both prime, else b(n)=0. This latter sequence has as its inverse Moebius transform the sequence c(n) = the number of distinct factors of n which are the smaller of a pair of twin primes. For example, c(15)=2 because 15 is divisible by 3 and 5, each of which is the smaller of a pair of twin primes.  Jonathan Vos Post, Jan 07 2005


LINKS

Table of n, a(n) for n=1..105.


FORMULA

a(n) = A062301(n+1) = 1  A100810(n).


MATHEMATICA

Table[If[Prime[n] + 2 == Prime[n + 1], 1, 0], {n, 120}] (* Ray Chandler, Jan 09 2005 *)


CROSSREFS

Sequence in context: A283991 A327861 A131929 * A139689 A204175 A285255
Adjacent sequences: A100818 A100819 A100820 * A100822 A100823 A100824


KEYWORD

easy,nonn


AUTHOR

Giovanni Teofilatto, Jan 06 2005


EXTENSIONS

Corrected and extended by Ray Chandler, Jan 09 2005


STATUS

approved



