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Heinz numbers of even-length integer partitions of even numbers.
16

%I #22 Jul 28 2024 16:38:56

%S 1,4,9,10,16,21,22,25,34,36,39,40,46,49,55,57,62,64,81,82,84,85,87,88,

%T 90,91,94,100,111,115,118,121,129,133,134,136,144,146,155,156,159,160,

%U 166,169,183,184,187,189,194,196,198,203,205,206,210,213,218,220

%N Heinz numbers of even-length integer partitions of even numbers.

%C The Heinz number of a partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k), so these are positive integers whose number of prime indices and sum of prime indices are both even, counting multiplicity in both cases.

%C A multiplicative semigroup: if m and n are in the sequence, then so is m*n. - _Antti Karttunen_, Jul 28 2024

%H Antti Karttunen, <a href="/A340784/b340784.txt">Table of n, a(n) for n = 1..20000</a>

%H <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>

%F Intersection of A028260 and A300061.

%e The sequence of partitions together with their Heinz numbers begins:

%e 1: () 57: (8,2) 118: (17,1)

%e 4: (1,1) 62: (11,1) 121: (5,5)

%e 9: (2,2) 64: (1,1,1,1,1,1) 129: (14,2)

%e 10: (3,1) 81: (2,2,2,2) 133: (8,4)

%e 16: (1,1,1,1) 82: (13,1) 134: (19,1)

%e 21: (4,2) 84: (4,2,1,1) 136: (7,1,1,1)

%e 22: (5,1) 85: (7,3) 144: (2,2,1,1,1,1)

%e 25: (3,3) 87: (10,2) 146: (21,1)

%e 34: (7,1) 88: (5,1,1,1) 155: (11,3)

%e 36: (2,2,1,1) 90: (3,2,2,1) 156: (6,2,1,1)

%e 39: (6,2) 91: (6,4) 159: (16,2)

%e 40: (3,1,1,1) 94: (15,1) 160: (3,1,1,1,1,1)

%e 46: (9,1) 100: (3,3,1,1) 166: (23,1)

%e 49: (4,4) 111: (12,2) 169: (6,6)

%e 55: (5,3) 115: (9,3) 183: (18,2)

%t primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];

%t Select[Range[100],EvenQ[PrimeOmega[#]]&&EvenQ[Total[primeMS[#]]]&]

%o (PARI)

%o A056239(n) = { my(f); if(1==n, 0, f=factor(n); sum(i=1, #f~, f[i, 2] * primepi(f[i, 1]))); }

%o A353331(n) = ((!(bigomega(n)%2)) && (!(A056239(n)%2)));

%o isA340784(n) = A353331(n); \\ _Antti Karttunen_, Apr 14 2022

%Y Note: A-numbers of Heinz-number sequences are in parentheses below.

%Y The case of prime powers is A056798.

%Y These partitions are counted by A236913.

%Y The odd version is A160786 (A340931).

%Y A000009 counts partitions into odd parts (A066208).

%Y A001222 counts prime factors.

%Y A047993 counts balanced partitions (A106529).

%Y A056239 adds up prime indices.

%Y A058695 counts partitions of odd numbers (A300063).

%Y A061395 selects the maximum prime index.

%Y A072233 counts partitions by sum and length.

%Y A112798 lists the prime indices of each positive integer.

%Y - Even -

%Y A027187 counts partitions of even length/maximum (A028260/A244990).

%Y A034008 counts compositions of even length.

%Y A035363 counts partitions into even parts (A066207).

%Y A058696 counts partitions of even numbers (A300061).

%Y A067661 counts strict partitions of even length (A030229).

%Y A339846 counts factorizations of even length.

%Y A340601 counts partitions of even rank (A340602).

%Y A340785 counts factorizations into even factors.

%Y A340786 counts even-length factorizations into even factors.

%Y Cf. A026424, A257541, A300272, A326837, A326845, A340385 (A340386), A340604, A353331 (characteristic function), A353332, A353333, A353334.

%Y Squares (A000290) is a subsequence.

%Y Not a subsequence of A329609 (30 is the first term of A329609 not occurring here, and 210 is the first term here not present in A329609).

%Y Positions of even terms in A373381.

%K nonn

%O 1,2

%A _Gus Wiseman_, Jan 30 2021