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

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A284168 Integers n such that sigma(binomial(n,k)) = sigma(binomial(n-1,k-1)) + sigma(binomial(n-1,k)) for some k. 1
3, 6, 15, 25, 27, 30, 35, 40, 48, 50, 54, 60, 63, 66, 78, 80, 100, 108, 112, 118, 120, 123, 124, 126, 140, 144, 158, 175, 192, 198, 200, 207, 216, 220, 224, 225, 232, 238, 243, 247, 304, 310, 316, 319, 341, 345, 348, 358, 364, 368, 375, 385, 391, 408, 416, 425, 432 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Consider the triangle formed by replacing each m in Pascal's triangle with sigma(m). Then this sequence consists of the row indices where there is a term that is equal to the sum of its NW and N neighbors as in a Pascal triangle.

LINKS

Table of n, a(n) for n=1..57.

EXAMPLE

Here is the triangle also described in A074801.

1,

1, 1,

1, 3, 1,

1, 4, 4, 1,

1, 7, 12, 7, 1,

1, 6, 18, 18, 6, 1,

On row index 3, we have 4 which is the sum of 1 and 3 its NW and N neighbors.

So a(1)= 3, and its column index is 1 which will be corresponding value in A284169.

PROG

(PARI) T(n, k) = sigma(binomial(n, k));

isokT(n, k) = T(n-1, k-1) + T (n-1, k) == T(n, k);

isokn(n) = for (k=1, n-1, if (isokT(n, k), return(1)));

CROSSREFS

Cf. A000203, A007318, A074801, A284169.

Sequence in context: A286502 A287101 A287189 * A216304 A020991 A079825

Adjacent sequences:  A284165 A284166 A284167 * A284169 A284170 A284171

KEYWORD

nonn

AUTHOR

Michel Marcus, Mar 21 2017

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 11 17:59 EST 2019. Contains 329925 sequences. (Running on oeis4.)