The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 60th year, we have over 367,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A205881 Second pentagonal numbers that are interprime. 1
 15, 26, 260, 495, 610, 950, 1190, 1962, 2420, 2667, 3197, 3337, 3480, 6370, 7597, 14455, 15965, 18205, 39447, 42926, 43947, 50325, 57135, 63140, 64377, 65000, 66255, 74037, 78090, 82251, 86520, 87967, 106267, 107870, 121980, 125426, 136957, 140607, 153760 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Intersection of A005449 and A024675. Also see references in A075190 about interprimes of different forms. LINKS Zak Seidov, Table of n, a(n) for n = 1..1000 EXAMPLE a(1) = 15 = A024675(5) = A005449(3). a(2) = 26 = A024675(8) = A005449(4). MATHEMATICA Select[Mean/@Partition[Prime[Range[15000]], 2, 1], IntegerQ[(Sqrt[1+24#]-1)/6]&] (* Harvey P. Dale, Feb 02 2020 *) CROSSREFS Cf. A005449, A024675, A075190. Sequence in context: A097963 A063936 A240914 * A132452 A063552 A131541 Adjacent sequences: A205878 A205879 A205880 * A205882 A205883 A205884 KEYWORD nonn AUTHOR Zak Seidov, Feb 01 2012 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 3 03:10 EST 2023. Contains 367531 sequences. (Running on oeis4.)