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A056996 Positive integers not of the form sigma(k) + phi(k) - 2k for some k. 5
5, 11, 19, 21, 23, 27, 33, 35, 39, 43, 45, 47, 51, 53, 55, 59, 67, 69, 71, 79, 81, 83, 87, 95, 99, 101, 103, 105, 107, 113, 115, 117, 119, 123, 129, 131, 135, 139, 141, 143, 147, 151, 153, 155, 159, 165, 167, 171, 173, 175, 177, 179, 185, 187, 189, 191, 193, 195 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Under the assumption that every even integer >= 18 is the sum of three distinct primes, all elements of this sequence are odd. See A278373 for more details.

LINKS

David W. Wilson, Table of n, a(n) for n = 1..10000

MATHEMATICA

Take[#, 59] &@ Complement[Range@ #, Union@ Table[DivisorSigma[1, n] + EulerPhi@ n - 2 n, {n, #}]] &[10^5] (* Michael De Vlieger, Nov 30 2016 *)

CROSSREFS

Complement is A278373.

Cf. A000010 (phi), A000203 (sigma).

Sequence in context: A048253 A102174 A140515 * A102184 A290751 A320518

Adjacent sequences:  A056993 A056994 A056995 * A056997 A056998 A056999

KEYWORD

nonn

AUTHOR

David W. Wilson, Sep 06 2000

STATUS

approved

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Last modified September 27 19:23 EDT 2021. Contains 347694 sequences. (Running on oeis4.)