login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A142719 a(n) = if n < 41 then n^2 - n + 41, otherwise n^2 - 81*n + 1681. 3
41, 41, 43, 47, 53, 61, 71, 83, 97, 113, 131, 151, 173, 197, 223, 251, 281, 313, 347, 383, 421, 461, 503, 547, 593, 641, 691, 743, 797, 853, 911, 971, 1033, 1097, 1163, 1231, 1301, 1373, 1447, 1523, 1601, 41, 43, 47, 53, 61, 71, 83, 97, 113, 131, 151, 173, 197 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A variation on Euler's prime generating polynomial found in a novel by Arthur C. Clarke and Gentry Lee. Gives 96 primes in first 100 terms.

Note that in n^2-81*n+1681, substitution of n= m+41 gives m^2+m+41, Euler's polynomial. So we get the same set of 40 primes twice.

REFERENCES

Arthur C. Clarke and Gentry Lee, The Garden of Rama, Dell Publishing, 1991, ISBN 0-533-29817-8, page 59.

LINKS

Table of n, a(n) for n=1..54.

James Clewett and Brady Haran, 41 and more Ulam's Spiral, Numberphile video, 2013.

FORMULA

a(n)=If[n < 41, n^2 - n + 41, n^2 - 81*n + 1681].

MATHEMATICA

f[n_]=If[n<41, n^2-n+41, n^2-81*n+1681]; Table[f[n], {n, 0, 100}]

CROSSREFS

Cf. A005846.

Sequence in context: A155769 A247390 A291501 * A284043 A191754 A165862

Adjacent sequences:  A142716 A142717 A142718 * A142720 A142721 A142722

KEYWORD

nonn

AUTHOR

Roger L. Bagula, Sep 27 2008

EXTENSIONS

Edited by N. J. A. Sloane, Sep 27 2008

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 November 14 02:19 EST 2019. Contains 329108 sequences. (Running on oeis4.)