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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A219109 The smallest k such that prime(k) == -1 (mod n). 3
1, 2, 1, 2, 8, 3, 6, 4, 7, 8, 14, 5, 27, 6, 10, 11, 19, 7, 12, 8, 13, 14, 33, 9, 35, 27, 16, 23, 40, 10, 18, 11, 32, 19, 34, 20, 21, 12, 51, 22, 38, 13, 55, 14, 24, 33, 60, 15, 25, 35, 26, 27, 47, 16, 29, 39, 30, 40, 71, 17, 93, 18, 54, 31, 77, 32, 79, 19, 33, 34, 61, 20, 172, 21, 35, 36 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Numbers n such that a(n) + 1 = a(n + 1) where the a(n)-th prime is not the smaller prime in a twin prime pair: 1, 3, 122, 267, 356, 362, 392, 403, 416, 446, 514, ....

Primes p(n) such that p is not -1 mod n for all prime p < p(n): 2, 3, 11, 31, 41, 59, 83, 97, 101, 109, 167, 191, 211, 277, 283, 313, 331, 367, 419,... Also primes p(n) such that p(n) <= A038700(n).

LINKS

Paolo P. Lava, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = A000720(A038700(n)). - Joerg Arndt, Apr 16 2013

EXAMPLE

For n = 11, we see that the 14th prime (43), modulo 11 is 10, or -1, so a(11) = 14.

MAPLE

with(numtheory); A219109:=proc(q) local k, n;

for n from 1 to q do k:=1; while (ithprime(k)+1) mod n>0 do k:=k+1; od;

print(k); od; end: A219109(10^6); # Paolo P. Lava, May 02 2013

PROG

(PARI) a(n)=forstep(t=n-1, n^99, n, if(isprime(t), return(primepi(t)))) \\ Charles R Greathouse IV, Mar 17 2014

CROSSREFS

Cf. A038700, A221861.

Sequence in context: A140894 A208747 A221878 * A137305 A282885 A242841

Adjacent sequences:  A219106 A219107 A219108 * A219110 A219111 A219112

KEYWORD

nonn

AUTHOR

Irina Gerasimova, Apr 11 2013

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 October 21 16:12 EDT 2019. Contains 328301 sequences. (Running on oeis4.)