The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A057570 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A057570

Numbers of the form n*(7n+-1)/2.
(history; published version)

#48 by Harvey P. Dale at Sun Sep 17 15:50:52 EDT 2023

STATUS

editing

approved

#47 by Harvey P. Dale at Sun Sep 17 15:50:50 EDT 2023

MATHEMATICA

LinearRecurrence[{1, 2, -2, -1, 1}, {0, 3, 4, 13, 15}, 50] (* Harvey P. Dale, Sep 17 2023 *)

STATUS

approved

editing

#46 by Bruno Berselli at Thu Mar 17 07:03:07 EDT 2022

STATUS

proposed

approved

#45 by Amiram Eldar at Thu Mar 17 06:14:59 EDT 2022

STATUS

editing

proposed

#44 by Amiram Eldar at Thu Mar 17 06:09:41 EDT 2022

FORMULA

Sum_{n>=2} 1/a(n) = 14 - 2*cot(Pi/7)*Pi. - Amiram Eldar, Mar 17 2022

STATUS

approved

editing

#43 by Bruno Berselli at Wed Oct 07 11:09:39 EDT 2015

STATUS

editing

approved

#42 by Bruno Berselli at Wed Oct 07 11:08:50 EDT 2015

FORMULA

a(n) = +1*a(n-1)+2*a(n-2)-2*a(n-3)-1*a(n-4)+1*a(n-5). - _Joerg Arndt_, Jan 25 2011

a(n) = (14*n*(n-1)+5*(2*n-1)*(-1)^n+5)/16. a(n)-a(n-2) = A047341(n-1) for n>2. - Bruno Berselli, Jan 25 2011

a(n)-a(n-2) = A047341(n-1) for n>2. - Bruno Berselli, Jan 25 2011

#41 by Bruno Berselli at Wed Oct 07 11:06:36 EDT 2015

COMMENTS

Sequence provides all integers m such that 56*m + 1 is a square. [Bruno Berselli, Oct 07 2015]

STATUS

approved

editing

#40 by Charles R Greathouse IV at Thu Sep 24 11:48:28 EDT 2015

STATUS

editing

approved

#39 by Charles R Greathouse IV at Thu Sep 24 11:48:26 EDT 2015

PROG

(PARI) a(n)=(14*n*(n-1)+5*(2*n-1)*(-1)^n+5)/16 \\ Charles R Greathouse IV, Sep 24 2015

STATUS

approved

editing