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 A126796 Number of complete partitions of n. 48
 1, 1, 1, 2, 2, 4, 5, 8, 10, 16, 20, 31, 39, 55, 71, 100, 125, 173, 218, 291, 366, 483, 600, 784, 971, 1244, 1538, 1957, 2395, 3023, 3693, 4605, 5604, 6942, 8397, 10347, 12471, 15235, 18309, 22267, 26619, 32219, 38414, 46216, 54941, 65838, 77958, 93076, 109908 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS A partition of n is complete if every number 1 to n can be represented as a sum of parts of the partition. This generalizes perfect partitions, where the representation for each number must be unique. A partition is complete iff each part is no more than 1 more than the sum of all smaller parts. (This includes the smallest part, which thus must be 1.) - Franklin T. Adams-Watters, Mar 22 2007 For n > 0: a(n) = sum of n-th row in A261036 and also a(floor(n/2)) = A261036(n,floor((n+1)/2). - Reinhard Zumkeller, Aug 08 2015 a(n+1) is the number of partitions of n such that each part is no more than 2 more than the sum of all smaller parts (generalizing Adams-Watters's criterion). Bijection: each partition counted by a(n+1) must contain a 1, removing that gives a desired partition of n. - Brian Hopkins, May 16 2017 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..10000 (first 301 terms from David W. Wilson) George E. Andrews, George Beck, and Brian Hopkins, On a Conjecture of Hanna Connecting Distinct Part and Complete Partitions, Annals of Comb., 24(2020), pp. 217-224. George Beck and Shane Chern, Reciprocity between partitions and compositions, arXiv:2108.04363 [math.CO], 2021. SeungKyung Park, Complete Partitions, Fibonacci Quarterly, Vol. 36 (1998), pp. 354-360. FORMULA G.f.: 1 = Sum_{n>=0} a(n)*x^n*Product_{k=1..n+1} (1-x^k). - Paul D. Hanna, Mar 08 2012 a(n) ~ exp(Pi*sqrt(2*n/3)) / (4*sqrt(3)*n) * (1 - (sqrt(3/2)/Pi + 25*Pi/(24*sqrt(6))) / sqrt(n) + (25/16 - 1679*Pi^2/6912)/n). - Vaclav Kotesovec, May 24 2018, extended Nov 02 2019 EXAMPLE There are a(5) = 4 complete partitions of 5:   [1, 1, 1, 1, 1], [1, 1, 1, 2], [1, 2, 2], and [1, 1, 3]. G.f.: 1 = 1*(1-x) + 1*x*(1-x)*(1-x^2) + 1*x^2*(1-x)*(1-x^2)*(1-x^3) + 2*x^3*(1-x)*(1-x^2)*(1-x^3)*(1-x^4) + 2*x^4*(1-x)*(1-x^2)*(1-x^3)*(1-x^4)*(1-x^5) + ... MAPLE isCompl := proc(p, n) local m, pers, reps, f, lst, s; reps := {}; pers := combinat[permute](p); for m from 1 to nops(pers) do lst := op(m, pers); for f from 1 to nops(lst) do s := add( op(i, lst), i=1..f); reps := reps union {s}; od; od; for m from 1 to n do if not m in reps then RETURN(false); fi; od; RETURN(true); end: A126796 := proc(n) local prts, res, p; prts := combinat[partition](n); res :=0; for p from 1 to nops(prts) do if isCompl(op(p, prts), n) then res := res+1; fi; od; RETURN(res); end: for n from 1 to 40 do printf("%d %d ", n, A126796(n)); od; # R. J. Mathar, Feb 27 2007 # At the beginning of the 2nd Maple program replace the current 15 by any other positive integer n in order to obtain a(n). - Emeric Deutsch, Mar 04 2007 with(combinat): a:=proc(n) local P, b, k, p, S, j: P:=partition(n): b:=0: for k from 1 to numbpart(n) do p:=powerset(P[k]): S:={}: for j from 1 to nops(p) do S:=S union {add(p[j][i], i=1..nops(p[j]))} od: if nops(S)=n+1 then b:=b+1 else b:=b: fi: od: end: seq(a(n), n=1..30); # Emeric Deutsch, Mar 04 2007 with(combinat): n:=15: P:=partition(n): b:=0: for k from 1 to numbpart(n) do p:=powerset(P[k]): S:={}: for j from 1 to nops(p) do S:=S union {add(p[j][i], i=1..nops(p[j]))} od: if nops(S)=n+1 then b:=b+1 else b:=b: fi: od: b; # Emeric Deutsch, Mar 04 2007 MATHEMATICA T[n_, k_] := T[n, k] = If[k <= 1, 1, If[n < 2k-1, T[n, Floor[(n+1)/2]], T[n, k-1] + T[n-k, k]]]; a[n_] := T[n, Floor[(n+1)/2]]; Table[a[n], {n, 0, 50}] (* Jean-François Alcover, Apr 11 2017, after Franklin T. Adams-Watters *) PROG (PARI) {T(n, k)=if(k<=1, 1, if(n<2*k-1, T(n, floor((n+1)/2)), T(n, k-1)+T(n-k, k)))} {a(n)=T(n, floor((n+1)/2))} /* If modified to save earlier results, this would be efficient. */ /* Franklin T. Adams-Watters, Mar 22 2007 */ (PARI) /* As coefficients in g.f.: */ {a(n)=local(A=[1, 1]); for(i=1, n+1, A=concat(A, 0); A[#A]=polcoeff(1-sum(m=1, #A, A[m]*x^m*prod(k=1, m, 1-x^k +x*O(x^#A))), #A) ); A[n+1]} for(n=0, 50, print1(a(n), ", ")) /* Paul D. Hanna, Mar 06 2012 */ (Haskell) import Data.MemoCombinators (memo3, integral, Memo) a126796 n = a126796_list !! n a126796_list = map (pMemo 1 1) [0..] where    pMemo = memo3 integral integral integral p    p _ _ 0 = 1    p s k m      | k > min m s = 0      | otherwise   = pMemo (s + k) k (m - k) + pMemo s (k + 1) m -- Reinhard Zumkeller, Aug 07 2015 CROSSREFS Cf. A002033, A188431, A209405. Cf. A261036. Cf. A286929, A286097. Sequence in context: A240486 A237871 A027193 * A325831 A240451 A206138 Adjacent sequences:  A126793 A126794 A126795 * A126797 A126798 A126799 KEYWORD nonn,nice AUTHOR Brian Hopkins, Feb 20 2007 EXTENSIONS More terms from R. J. Mathar, Feb 27 2007 More terms from Emeric Deutsch, Mar 04 2007 Further terms from Franklin T. Adams-Watters and David W. Wilson, Mar 22 2007 STATUS approved

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Last modified October 4 12:06 EDT 2022. Contains 357239 sequences. (Running on oeis4.)