A076667 antisigma(n) + antisigma(n+3) = antisigma(n+1) + antisigma(n+2), where antisigma(n) = sum of the non-divisors of n that are between 1 and n.

6, 907, 1359, 2512, 26545, 6094105, 10714840, 11967486, 36282316, 45123265, 60144196, 113547460, 318424060, 474656416, 488176150, 920250976, 927186976, 993590680, 2509123036, 3015854296, 3966424141, 4168017460, 4360145356

Offset

1,1

Comments

Each term of the sequence marks the start of four consecutive antisigma-values for which the sum of the means equals the sum of the extremes.

Links

Table of n, a(n) for n=1..23.

Example

antisigma(6) + antisigma(9) = 9 + 32 = 41; antisigma(7) + antisigma(8) = 20 + 21 = 41, so 6 is a term of the sequence.

Mathematica

antisigma[n_] := (n (n + 1) / 2) - DivisorSigma[1, n]; Select[Range[10^5], antisigma[ # ] + antisigma[ # + 3] == antisigma[ # + 1] + antisigma[ # + 2] &]

Crossrefs

Sequence in context: A180992 A229629 A137801 * A000652 A214638 A175554

Adjacent sequences: A076664 A076665 A076666 * A076668 A076669 A076670

Keyword

nonn

Author

Joseph L. Pe, Oct 25 2002

Extensions

a(6)-a(23) from Donovan Johnson, Dec 02 2009

Status

approved