A056996 - OEIS

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A056996

Positive integers not of the form sigma(k) + phi(k) - 2k for some k.

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

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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