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A141426 Count of numbers smaller than and coprime to the prime A140555(n). 4
1, 2, 18, 28, 42, 58, 70, 78, 88, 108, 112, 126, 136, 138, 148, 162, 178, 180, 196, 198, 210, 228, 238, 240, 268, 280, 282, 292, 312, 316, 336, 348, 358, 378, 388, 396, 400, 408, 418, 420, 430, 438, 448, 462, 466, 478, 486, 490, 498, 508, 520, 522, 546, 568 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

FORMULA

a(n) = phi(A140555(n)) = A140555(n) - 1.

MAPLE

isA140555 := proc(n) RETURN( isprime(n) and not isprime(n+6) ) ; end: A140555 := proc(n) option remember ; if n = 1 then 2; else for a from procname(n-1)+1 do if isA140555(a) then RETURN(a) ; fi; od: fi; end: A141426 := proc(n) A140555(n)-1 ; end: for n from 1 to 100 do printf("%d, ", A141426(n)) ; od: # R. J. Mathar, Aug 12 2008

CROSSREFS

Cf. A140555.

Sequence in context: A115042 A191461 A098561 * A101844 A193598 A190047

Adjacent sequences:  A141423 A141424 A141425 * A141427 A141428 A141429

KEYWORD

nonn

AUTHOR

Giovanni Teofilatto, Aug 06 2008

EXTENSIONS

Edited and extended by R. J. Mathar, Aug 12 2008

STATUS

approved

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Last modified July 15 14:28 EDT 2019. Contains 325031 sequences. (Running on oeis4.)