A090973 -id:A090973 - cp's OEIS frontend

A038606 Least k such that k-th prime > n * k.

1, 5, 12, 31, 69, 181, 443, 1052, 2701, 6455, 15928, 40073, 100362, 251707, 637235, 1617175, 4124437, 10553415, 27066974, 69709680, 179992909, 465769803, 1208198526, 3140421716, 8179002096, 21338685407, 55762149030, 145935689361, 382465573483, 1003652347100

Offset: 1

Vasiliy Danilov (danilovv(AT)usa.net) 1998 Jul

nonn

Log(a(n)) =~ -1.295 + 0.964312n. - Robert G. Wilson v, Jan 25 2002
Numbers n such that prime(n) (mod n) begins the next cycle of terms in A004648. Generally prime(i) (mod i) exceeds prime(i-1) (mod i-1) but there are numerous times where for a short run prime(i) (mod i) is minimally less than its predecessor. Here n is substantially less. See Labos's graph.
A090973(a(n)) = n+1. [From Reinhard Zumkeller, Aug 16 2009]
With offset 2: Index j of prime p(j) such that ceiling[p(j)/j]=n is first satisfied. a(n) = A062742(n) = A038624(n) for n >= 3. [From Jaroslav Krizek, Dec 13 2009]

Giovanni Resta, Table of n, a(n) for n = 1..50
Labos, E. Graph of first 50000 terms of A004648
Andrew R. Booker, The Nth Prime Page

Cf. A038607, A004648, A038625.

A038606 := proc(n)
    for k from 1 do
        if ithprime(k)> n*k then
            return k;
        end if;
    end do:
end proc: # R. J. Mathar, Aug 24 2013

k = 1; Do[ While[ Floor[ Prime[k]/k] < n, k++ ]; Print[k]; k++, {n, 1, 30} ]

k=1;n=1;forprime(p=3,4e9,if(p/n++>k,print1(n", ");k++)) \\ Charles R Greathouse IV, Sep 06 2011

a(n) = pi(A038607(n)) = A000720(A038607(n)).

Edited by Robert G. Wilson v, Jan 25 2002
a(21)=179992909 corrected by Ray Chandler, Dec 01 2004
a(29)-a(30) from Charles R Greathouse IV, Sep 06 2011
a(31)-a(50) obtained from the values of A038625 computed by Jan Büthe. - Giovanni Resta, Sep 01 2018

A068901 Least number that when added to the n-th prime gives a multiple of n.

Original entry on oeis.org

0, 1, 1, 1, 4, 5, 4, 5, 4, 1, 2, 11, 11, 13, 13, 11, 9, 11, 9, 9, 11, 9, 9, 7, 3, 3, 5, 5, 7, 7, 28, 29, 28, 31, 26, 29, 28, 27, 28, 27, 26, 29, 24, 27, 28, 31, 24, 17, 18, 21, 22, 21, 24, 19, 18, 17, 16, 19, 18, 19, 22, 17, 8, 9, 12, 13, 4, 3, 67, 1

Offset: 1

Reinhard Zumkeller, Mar 05 2002

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Cf. A090973. - Reinhard Zumkeller, Aug 16 2009

Cf. A000040, A068902.

a068901 n = head $
   filter ((== 0) . (`mod` fromIntegral n) . (+ a000040 n)) $ [0..]
-- Reinhard Zumkeller, Feb 18 2012

f[n_] := Module[{p=Prime[n]}, n*Ceiling[p/n]-p]; Array[f,100]  (* Harvey P. Dale, Apr 06 2011 *)

a(n) = Min_{k | n divides (prime(n)+k)}.
a(n) = A068902(n) - A000040(n).
a(n) = n*ceiling(prime(n)/n) - prime(n). - Vladeta Jovovic, Apr 06 2003

cp's OEIS Frontend

A038606 Least k such that k-th prime > n * k.

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