cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A300385 In the ranked poset of integer partitions ordered by refinement, number of maximal chains from the partition with Heinz number n to the local maximum.

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%I A300385 #22 Oct 07 2018 19:31:30
%S A300385 0,1,1,1,1,1,1,1,1,1,1,2,1,1,1,2,1,2,1,2,1,1,1,4,1,1,1,2,1,3,1,4,1,1,
%T A300385 1,6,1,1,1,5,1,3,1,2,2,1,1,11,1,2,1,2,1,5,1,5,1,1,1,9,1,1,2,11,1,3,1,
%U A300385 2,1,3,1,19,1,1,2,2,1,3,1,14,2,1,1,10,1,1,1,5,1,10,1,2,1,1,1,33,1,2,2,7,1,3,1,5,3
%N A300385 In the ranked poset of integer partitions ordered by refinement, number of maximal chains from the partition with Heinz number n to the local maximum.
%C A300385 The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k).
%H A300385 Antti Karttunen, <a href="/A300385/b300385.txt">Table of n, a(n) for n = 1..12288</a>
%H A300385 Antti Karttunen, <a href="/A300385/a300385.txt">Data supplement: n, a(n) computed for n = 1..100000</a>
%H A300385 <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>
%H A300385 <a href="/index/He#Heinz">Index entries for sequences related to Heinz numbers</a>
%F A300385 a(1) = 0; for n > 1, if A001222(n) <= 2 [when n is a prime or semiprime], a(n) = 1, otherwise, a(n) = Sum_{p|n} Sum_{q|n, q>=(p+[p^2 does not divide n])} a(prime(primepi(p)+primepi(q)) * (n/(p*q))), where p ranges over all distinct primes dividing n, and q also ranges over primes dividing n, but with condition that q > p if p is a unitary prime factor of n, otherwise q >= p. Here primepi = A000720. - _Antti Karttunen_, Oct 07 2018
%e A300385 The a(36) = 6 maximal chains are the rows:
%e A300385 (2211)<(222)<(42)<(6)
%e A300385 (2211)<(411)<(42)<(6)
%e A300385 (2211)<(411)<(51)<(6)
%e A300385 (2211)<(321)<(42)<(6)
%e A300385 (2211)<(321)<(51)<(6)
%e A300385 (2211)<(321)<(33)<(6)
%t A300385 chc[ptn_]:=If[Length[ptn]===1,1,Total[chc/@Union[ReplaceList[ptn,{a___,x_,b___,y_,c___}:>Sort[{x+y,a,b,c},Greater]]]]];
%t A300385 primeMS[n_]:=If[n===1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
%t A300385 Table[chc[Reverse[primeMS[n]]],{n,100}]
%o A300385 (PARI) A300385(n) = if(1==n,0,if(bigomega(n)<=2,1,my(f=factor(n), u = #f~, s = 0); for(i=1,u,for(j=i+(1==f[i,2]),u, s += A300385((n/(f[i,1]*f[j,1])*prime(primepi(f[i,1])+primepi(f[j,1])))))); (s))); \\ _Antti Karttunen_, Oct 06 2018
%o A300385 (PARI)
%o A300385 memoA300385 = Map();
%o A300385 A300385(n) = if(1==n,0,if(bigomega(n)<=2,1,if(mapisdefined(memoA300385,n),mapget(memoA300385,n),my(f=factor(n), u = #f~, s = 0); for(i=1,u,for(j=i+(1==f[i,2]),u, s += A300385(prime(primepi(f[i,1])+primepi(f[j,1]))*(n/(f[i,1]*f[j,1]))))); mapput(memoA300385,n,s); (s)))); \\ (A memoized implementation). - _Antti Karttunen_, Oct 07 2018
%Y A300385 Cf. A000041, A001055, A001222, A002846, A056239, A112798, A213427, A215366, A265947, A296150, A299200, A299202, A299925, A300273, A300383, A300384.
%K A300385 nonn
%O A300385 1,12
%A A300385 _Gus Wiseman_, Mar 04 2018
%E A300385 More terms from _Antti Karttunen_, Oct 06 2018