login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A165571 Lesser prime factor of successively better golden semiprimes. 5
2, 3, 7, 19, 23, 29, 97, 353, 563, 631, 919, 1453, 2207, 15271, 15737, 42797, 49939, 133559, 179317, 287557, 508451, 918011, 1103483, 1981891, 9181097, 16958611, 17351447, 52204391, 66602803, 99641617, 134887397, 487195147, 629449511, 943818943, 1527963169, 2048029369 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

See A165569 and A165570 for the definition. Probably a subset of A108541.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..48

FORMULA

a(n) = A000040(A165569(n)).

a(n) = A165570(n)/A165572(n).

MATHEMATICA

f[p_] := Module[{x = GoldenRatio * p, p1, p2}, p1 = NextPrime[x, -1]; p2 = NextPrime[p1]; If[p2 - x > x - p1, p1, p2]]; seq={}; dm = 1; p1 = 1; Do[p1 = NextPrime[p1]; k++; p2 = f[p1]; d = Abs[p2/p1 - GoldenRatio]; If[d < dm, dm = d; AppendTo[seq, p1]], {10^4}]; seq  (* Amiram Eldar, Nov 28 2019 *)

CROSSREFS

Cf. A108539, A165569, A165570, A165572.

Sequence in context: A073641 A273006 A117763 * A178954 A138111 A218100

Adjacent sequences:  A165568 A165569 A165570 * A165572 A165573 A165574

KEYWORD

nonn

AUTHOR

Antti Karttunen, Sep 22 2009

EXTENSIONS

a(16)-a(23) from Donovan Johnson, May 13 2010

a(24)-a(36) from Amiram Eldar, Nov 28 2019

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 2 20:38 EDT 2021. Contains 346428 sequences. (Running on oeis4.)