This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A026903 a(n) is the number of multisets S of positive integers satisfying E(S)=n, where E = 2nd elementary symmetric function. 2
 1, 1, 2, 2, 2, 3, 2, 3, 4, 3, 3, 5, 3, 4, 6, 4, 4, 6, 4, 6, 7, 4, 5, 9, 6, 6, 8, 6, 7, 9, 5, 9, 10, 6, 9, 12, 6, 8, 12, 9, 9, 12, 8, 11, 14, 8, 10, 15, 11, 12, 13, 10, 13, 16, 11, 15, 16, 8, 14, 21, 12, 14, 19, 14, 16, 18, 12, 17, 21, 14, 17, 23, 15, 19, 22 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Andrew Howroyd, Table of n, a(n) for n = 1..1000 Wikipedia, Elementary symmetric polynomial EXAMPLE a(9) = 4 counts {1,9},{3,3},{1,1,4},{1,1,1,2}. a(33) = 10 counts {1,1,1,1,1,1,3}, {1,1,1,2,2,2}, {1,1,1,10}, {1,1,2,7}, {1,1,4,4}, {1,1,16}, {1,2,2,5}, {1,33}, {3,3,4}, {3,11}. PROG (PARI) a(n)={my(recurse(lim, s1, s2)=if(s2==n, 1, sum(i=1, min((n-s2)\s1, lim), self()(i, s1+i, s2+s1*i)))); sum(i=1, n, recurse(i, i, 0))} \\ Andrew Howroyd, Dec 17 2018 CROSSREFS Cf. A026904. Sequence in context: A220415 A286565 A219354 * A253893 A289437 A068324 Adjacent sequences:  A026900 A026901 A026902 * A026904 A026905 A026906 KEYWORD nonn AUTHOR EXTENSIONS a(33) corrected by Laurance L. Y. Lau, Dec 17 2018 Terms a(35) and beyond from Andrew Howroyd, Dec 17 2018 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.

Last modified July 21 21:14 EDT 2019. Contains 325199 sequences. (Running on oeis4.)