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A275472 First differences of A275316. 2
945, 1575, 2520, 1008, 4500, 2640, 4416, 49104, 2160, 432, 9072, 5616, 28080, 10440, 8280, 16380, 8100, 18576, 4464, 15840, 5184, 123228, 26460, 25704, 3024, 68400, 31203, 31293, 15264, 110880, 12960, 0, 9720, 16200, 51840, 35640, 71880, 57288, 49032, 81000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The terms represent differences between consecutive amicable pair averages given in A275316.

Interestingly, the first two odd abundant numbers begin this sequence: a(1) = 945 = A005231(1) and a(2) = 1575 = A005231(2).

Of the first 141 terms, 4 are odd, 137 are even, 136 are abundant, 2 are deficient [specifically, a(27) = 31203 and a(28) = 31293], 7 numbers occur twice [specifically, a(53) = a(59) = 1728, a(25) = a(136) = 3024, a(21) = a(127) = 5184, a(31) = a(137) = 12960, a(34) = a(41) = 16200, a(74) = a(77) = 20736, and a(66) = a(104) = 156240], 3 numbers occur three times [specifically, a(32) = a(107) = a(139) = 0, a(35) = a(42) = a(52) = 51840, and a(30) = a(86) = a(97) = 110880], and every number is divisible by 3.

a(n) = A275066(n) for 41 of the first 141 indices: n = 1, 2, 3, 4, 5, 6, 7, 12, 13, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 36, 37, 38, 39, 43, 44, 48, 49, 50, 57, 58, 59, 64, 65, 95, 120, 121.

a(n) = -A275066(n) for 9 of the first 141 indices: n = 15, 41, 46, 55, 67, 70, 81, 86, 141.

LINKS

Timothy L. Tiffin, Table of n, a(n) for n = 1..141

VaxaSoftware, List of amicable numbers from 1 to 20,000,000 [142 pairs].

FORMULA

a(n) = A275316(n+1) - A275316(n).

EXAMPLE

a(9) = A275316(10) - A275316(9) = 69120 - 66960 = 2160.

CROSSREFS

Cf. A005231, A260086, A260087, A259933, A275066, A275316.

Sequence in context: A287646 A316116 A188439 * A275066 A127667 A252184

Adjacent sequences:  A275469 A275470 A275471 * A275473 A275474 A275475

KEYWORD

nonn

AUTHOR

Timothy L. Tiffin, Jul 29 2016

STATUS

approved

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Last modified May 19 22:32 EDT 2019. Contains 323411 sequences. (Running on oeis4.)