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A063500 a(n) is the least composite solution of phi(k + 6n) = phi(k) + 6n. 3
21, 45, 63, 95, 224, 135, 301, 95, 189, 161, 260, 115, 400, 165, 476, 195, 620, 145, 644, 203, 640, 285, 343, 155, 728, 185, 567, 155, 560, 301, 860, 185, 1000, 329, 1892, 235 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Next term (a(37)) exceeds 10^5 - Matthew Conroy, Sep 13 2001

Next term (a(37)), if it exists, exceeds 10^7. - David Wasserman, Jul 03 2002

If a(37) exists, it is larger than 7.6 * 10^11. - Jud McCranie, Aug 29 2013

a(37) > 10^13, if it exists. - Giovanni Resta, Feb 25 2020

LINKS

Table of n, a(n) for n=1..36.

FORMULA

Smallest values satisfying A000010(a(n)+6n)=A000010(a(n))+6n relation.

EXAMPLE

n=100, d=600=6n, a(100)=671=11*61, phi(671)=600, phi(671+600)=phi(1271)=(31-1)*(41-1)=600+600=phi(671)+d.

PROG

(PARI) for (n=1, 36, a=1; while (isprime(a) || eulerphi(a + 6*n) != eulerphi(a) + 6*n, a++); write("b063500.txt", n, " ", a) ) \\ Harry J. Smith, Aug 24 2009

CROSSREFS

Cf. A000010, A054904, A054905.

Sequence in context: A003857 A317210 A099468 * A102603 A147222 A199767

Adjacent sequences:  A063497 A063498 A063499 * A063501 A063502 A063503

KEYWORD

nonn,more

AUTHOR

Labos Elemer, Jul 30 2001

STATUS

approved

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Last modified May 25 20:58 EDT 2020. Contains 334597 sequences. (Running on oeis4.)