

A076666


Numbers n such that sigma(n) + sigma(n+3) = sigma(n+1) + sigma(n+2).


1



2012, 2096, 15892, 17888, 39916, 102784, 141008, 146227, 482144, 487865, 1321312, 1887008, 2749057, 3513881, 7141158, 16767172, 17503912, 28122834, 30534728, 37453779, 42140437, 60994100, 67777337, 78251933, 113091820, 113768920, 129868059, 199240914, 240859196, 302897372
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OFFSET

1,1


COMMENTS

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


LINKS

Giovanni Resta, Table of n, a(n) for n = 1..90 (terms < 4*10^12)


EXAMPLE

sigma(2012) + sigma(2015) = 3528 + 2688 = 6216; sigma(2013) + sigma(2014) = 2976 + 3240 = 6216, so 2012 is a term of the sequence.


MATHEMATICA

Select[Range[10^5], DivisorSigma[1, # ] + DivisorSigma[1, # + 3] == DivisorSigma[1, # + 1] + DivisorSigma[1, # + 2] &]


CROSSREFS

Cf. A000203, A055574, A065900, A073500, A099632, A226361, A226475.
Sequence in context: A020433 A191421 A250836 * A323470 A309918 A189188
Adjacent sequences: A076663 A076664 A076665 * A076667 A076668 A076669


KEYWORD

nonn


AUTHOR

Joseph L. Pe, Oct 25 2002


EXTENSIONS

a(6)a(26) from Donovan Johnson, Feb 01 2009
a(27)a(30) from Alex Ratushnyak, Jun 29 2013


STATUS

approved



