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A066902 Integers k such that phi(prime(k)+1) = phi(prime(k)-1). 2
3, 5, 20, 156, 254, 377, 593, 1800, 5903, 5981, 7925, 18669, 19240, 41274, 48296, 135700, 146866, 228028, 234303, 251216, 407377, 654288, 802222, 886223, 938654, 1063412, 1072766, 1212140, 1238668, 1515063, 1609346, 2080991, 2097725, 2363130, 2408674, 2916514 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Integers k such that A008331(k) = A008330(k).
LINKS
FORMULA
a(n) = primepi(A067890(n)). - Giovanni Resta, Apr 06 2020
MATHEMATICA
Select[Range[1000000], EulerPhi[Prime[#]-1]==EulerPhi[Prime[#]+1]&] (* Harvey P. Dale, Feb 25 2012 *)
PROG
(PARI) isok(k) = my(p=prime(k)); eulerphi(p+1) == eulerphi(p-1); \\ Michel Marcus, Apr 06 2020
CROSSREFS
Sequence in context: A197156 A171864 A256093 * A007363 A103991 A224994
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Jan 26 2002
EXTENSIONS
More terms from Harvey P. Dale, Feb 25 2012
More terms from Jinyuan Wang, Apr 05 2020
STATUS
approved

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Last modified June 21 20:04 EDT 2024. Contains 373559 sequences. (Running on oeis4.)