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A175897 Numbers n with property that n*prime(n)+(n+1)*prime(n+1) is a perfect square s^2. 1
1681, 3146, 5917, 308950, 10553441, 10553550, 4273262954, 9781980985 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Or, numbers n with property that A033286(n)+A033286(n+1) is a perfect square s^2, A033286(n)=n*(n-th prime). [From Zak Seidov, Oct 12 2010]

a(9) > pi(4*10^12). [From Donovan Johnson, Oct 22 2010]

LINKS

Table of n, a(n) for n=1..8.

EXAMPLE

{n,s}: {1681,6943},{3146,13487},{5917,26299},{308950,1647737}, {10553441,63320647},{10553550,63321299}; no more n's up to 2*10^8.

PROG

(PARI) isok(n) = issquare(n*prime(n)+(n+1)*prime(n+1)); \\ Michel Marcus, Oct 19 2013

CROSSREFS

Sequence in context: A221204 A145292 A228183 * A322745 A189654 A163009

Adjacent sequences:  A175894 A175895 A175896 * A175898 A175899 A175900

KEYWORD

more,nonn

AUTHOR

Zak Seidov, Oct 11 2010

EXTENSIONS

a(7)-a(8) from Donovan Johnson, Oct 22 2010

STATUS

approved

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Last modified June 4 02:07 EDT 2020. Contains 334812 sequences. (Running on oeis4.)