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A074927 a(n) such that p(n)*p(n+1)+a(n) is a minimal square. +0
5
3, 1, 1, 4, 1, 4, 1, 4, 9, 1, 9, 4, 1, 4, 9, 9, 1, 9, 4, 1, 9, 4, 9, 16, 4, 1, 4, 1, 4, 49, 4, 9, 1, 25, 1, 9, 9, 4, 9, 9, 1, 25, 1, 4, 1, 36, 36, 4, 1, 4, 9, 1, 25, 9, 9, 9, 1, 9, 4, 1, 25, 49, 4, 1, 4, 49, 9, 25, 1, 4, 9, 16, 9, 9, 4, 9, 16, 4, 16, 25, 1, 25, 1, 9, 4, 9, 16, 4, 1, 4, 36, 16, 4 (list; graph; listen)
OFFSET

1,1

COMMENT

When a(n)=1, p(n) and p(n+1) are twin primes.

a(n+1) = A072681(A024675(n)). [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Mar 04 2009]

FORMULA

For n>1: a(n) = ((p(n+1)-p(n))/2)^2. - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 22 2002

EXAMPLE

a(154) = 100 because p(154)*p(155) + 100 = 804509 = 897^2.

CROSSREFS

Sequence in context: A104610 A138684 A132442 this_sequence A139605 A098712 A023579

Adjacent sequences: A074924 A074925 A074926 this_sequence A074928 A074929 A074930

KEYWORD

nonn

AUTHOR

Zak Seidov (zakseidov(AT)yahoo.com), Oct 02 2002

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Last modified December 15 00:47 EST 2009. Contains 170825 sequences.


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