login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 5000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A173106 Partial sums of A005100. 1
1, 3, 6, 10, 15, 22, 30, 39, 49, 60, 73, 87, 102, 118, 135, 154, 175, 197, 220, 245, 271, 298, 327, 358, 390, 423, 457, 492, 529, 567, 606, 647, 690, 734, 779, 825, 872, 921, 971, 1022, 1074, 1127, 1182, 1239, 1297, 1356, 1417, 1479, 1542, 1606, 1671, 1738, 1806, 1875, 1946 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Partial sums of deficient numbers. The first 15 values are the same as the first 15 values of A025723 Index of 7^n within sequence of numbers of form 5^i*7^j. The subsequence of primes in the partial sum of deficient numbers begins: 3, 73, 197, 271, 457, 647, 971, 1297, 2731. The squares begin 1, 49, 529.

LINKS

Table of n, a(n) for n=1..55.

FORMULA

a(n) = SUM[i=1..n]A005100(i) = SUM[i=1..n] {k such that sigma(k) < 2k}.

EXAMPLE

a(66) = 1 + 2 + 3 + 4 + 5 + 7 + 8 + 9 + 10 + 11 + 13 + 14 + 15 + 16 + 17 + 19 + 21 + 22 + 23 + 25 + 26 + 27 + 29 + 31 + 32 + 33 + 34 + 35 + 37 + 38 + 39 + 41 + 43 + 44 + 45 + 46 + 47 + 49 + 50 + 51 + 52 + 53 + 55 + 57 + 58 + 59 + 61 + 62 + 63 + 64 + 65 + 67 + 68 + 69 + 71 + 73 + 74 + 75 + 76 +77 + 79 + 81 + 82 + 83 + 85 + 86.

MATHEMATICA

Accumulate[Select[Range[100], DivisorSigma[1, #]<2#&]]  (* Harvey P. Dale, Apr 11 2011 *)

CROSSREFS

Cf. A000040, A005100, A025723.

Sequence in context: A061304 A109442 A025723 * A022784 A025736 A022952

Adjacent sequences:  A173103 A173104 A173105 * A173107 A173108 A173109

KEYWORD

easy,nonn

AUTHOR

Jonathan Vos Post, Feb 09 2010

EXTENSIONS

Corrected and extended by Harvey P. Dale, Apr 11 2011.

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified December 11 06:55 EST 2016. Contains 279043 sequences.