cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

A147587 a(n) = 14*n + 7.

Original entry on oeis.org

7, 21, 35, 49, 63, 77, 91, 105, 119, 133, 147, 161, 175, 189, 203, 217, 231, 245, 259, 273, 287, 301, 315, 329, 343, 357, 371, 385, 399, 413, 427, 441, 455, 469, 483, 497, 511, 525, 539, 553, 567, 581, 595, 609, 623, 637, 651, 665, 679, 693, 707, 721, 735
Offset: 0

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Author

Paul Curtz, Nov 08 2008

Keywords

Comments

a(n+3) = 14*n + 49 is the sum of seven consecutive odd numbers starting with 2*n+1. - Wesley Ivan Hurt, Apr 11 2015
Numbers k such that 3^k + 1 is divisible by 547. - Bruno Berselli, Aug 22 2018
Sum of the numbers from 2*(n-1) to 2*(n+2). - Bruno Berselli, Oct 25 2018

Crossrefs

Programs

Formula

a(n) = a(n-1) + 14.
a(n) = A132355(2*n+2) - A132355(2*n+1) = 7*A005408(n).
a(n) = 28*n - a(n-1) for n>0, a(0)=7. - Vincenzo Librandi, Nov 24 2010
From Wesley Ivan Hurt, Apr 11 2015: (Start)
G.f.: 7*(1 + x)/(1 - x)^2.
a(n) = 2*a(n-1) - a(n-2). (End)
Sum_{n>=0} (-1)^n/a(n) = Pi/28 (A132744). - Amiram Eldar, Dec 13 2021
From Amiram Eldar, Nov 25 2024: (Start)
Product_{n>=0} (1 - (-1)^n/a(n)) = sqrt(2)*sin(3*Pi/14).
Product_{n>=0} (1 + (-1)^n/a(n)) = sqrt(2)*cos(3*Pi/14). (End)
a(n) = (n+4)^2 - (n-3)^2. - Alexander Yutkin, Mar 16 2025
E.g.f.: 7*exp(x)*(1 + 2*x). - Stefano Spezia, Mar 18 2025

Extensions

More terms from Vincenzo Librandi, Oct 23 2009

A387448 Decimal expansion of cos(Pi/28).

Original entry on oeis.org

9, 9, 3, 7, 1, 2, 2, 0, 9, 8, 9, 3, 2, 4, 2, 5, 8, 3, 5, 3, 3, 1, 4, 8, 2, 4, 1, 9, 4, 7, 3, 7, 8, 6, 9, 7, 1, 5, 2, 6, 3, 5, 4, 9, 5, 7, 8, 2, 0, 7, 3, 2, 1, 4, 9, 2, 7, 7, 5, 6, 5, 0, 2, 1, 5, 9, 5, 1, 0, 3, 8, 0, 9, 6, 8, 8, 9, 0, 9, 4, 4, 6, 6, 9, 0, 9, 9, 5, 7, 6, 4, 8, 7, 2, 7, 0, 6, 4, 3, 8, 2, 2, 3, 5, 4, 3, 0, 0, 9, 0, 4, 5, 5, 3, 7, 6, 6, 8
Offset: 0

Views

Author

R. J. Mathar, Aug 29 2025

Keywords

Examples

			0.99371220989324258353...
		

Crossrefs

Cf. A132744.

Formula

Equals sin(13*Pi/28) = sqrt( (A232735+1)/2 ) = 2F1(-1/14,1/14;1/2;1/2).
Largest of the 12 real-valued roots of 4096*x^12 -12288*x^10 +13568*x^8 -6656*x^6 +1376*x^4 -96*x^2 +1 =0.
Showing 1-2 of 2 results.