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.
%I A347442 #13 Oct 22 2023 16:43:32 %S A347442 1,1,1,2,1,1,1,3,2,1,1,3,1,1,1,5,1,3,1,3,1,1,1,3,2,1,3,3,1,1,1,7,1,1, %T A347442 1,8,1,1,1,3,1,1,1,3,3,1,1,8,2,3,1,3,1,4,1,3,1,1,1,3,1,1,3,11,1,1,1,3, %U A347442 1,1,1,11,1,1,3,3,1,1,1,8,5,1,1,3,1,1,1,3,1,4,1,3,1,1,1,9,1,3,3,8,1,1,1,3,1,1,1,12 %N A347442 Number of factorizations of n with integer reverse-alternating product. %C A347442 A factorization of n is a weakly increasing sequence of positive integers > 1 with product n. %C A347442 We define the alternating product of a sequence (y_1,...,y_k) to be Product_i y_i^((-1)^(i-1)). The reverse-alternating product is the alternating product of the reversed sequence. %H A347442 Antti Karttunen, <a href="/A347442/b347442.txt">Table of n, a(n) for n = 1..65537</a> %F A347442 a(2^n) = A000041(n). %e A347442 The a(n) factorizations for n = 4, 8, 16, 32, 36, 54, 64: %e A347442 (4) (8) (16) (32) (36) (54) (64) %e A347442 (2*2) (2*4) (2*8) (4*8) (6*6) (3*18) (8*8) %e A347442 (2*2*2) (4*4) (2*16) (2*18) (2*3*9) (2*32) %e A347442 (2*2*4) (2*2*8) (3*12) (3*3*6) (4*16) %e A347442 (2*2*2*2) (2*4*4) (2*2*9) (2*4*8) %e A347442 (2*2*2*4) (2*3*6) (4*4*4) %e A347442 (2*2*2*2*2) (3*3*4) (2*2*16) %e A347442 (2*2*3*3) (2*2*2*8) %e A347442 (2*2*4*4) %e A347442 (2*2*2*2*4) %e A347442 (2*2*2*2*2*2) %t A347442 facs[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[facs[n/d],Min@@#>=d&]],{d,Rest[Divisors[n]]}]]; %t A347442 revaltprod[q_]:=Product[Reverse[q][[i]]^(-1)^(i-1),{i,Length[q]}]; %t A347442 Table[Length[Select[facs[n],IntegerQ@*revaltprod]],{n,100}] %o A347442 (PARI) A347442(n, m=n, ap=1, e=0) = if(1==n, 1==denominator(ap), sumdiv(n, d, if((d>1)&&(d<=m), A347442(n/d, d, ap * d^((-1)^e), 1-e)))); \\ _Antti Karttunen_, Oct 22 2023 %Y A347442 The restriction to powers of 2 is A000041, reverse A344607. %Y A347442 Positions of 2's are A001248. %Y A347442 Positions of 1's are A005117. %Y A347442 Positions of non-1's are A013929. %Y A347442 Allowing any alternating product <= 1 gives A339846. %Y A347442 Allowing any alternating product > 1 gives A339890. %Y A347442 The non-reverse version is A347437. %Y A347442 The reciprocal version is A347438. %Y A347442 The even-length case is A347439. %Y A347442 Allowing any alternating product < 1 gives A347440. %Y A347442 The odd-length case is A347441, ranked by A347453. %Y A347442 The additive version is A347445, ranked by A347457. %Y A347442 The non-reverse additive version is A347446, ranked by A347454. %Y A347442 Allowing any alternating product >= 1 gives A347456. %Y A347442 The ordered version is A347463. %Y A347442 A038548 counts possible reverse-alternating products of factorizations. %Y A347442 A071321 gives the alternating sum of prime factors (reverse: A071322). %Y A347442 A236913 counts partitions of 2n with reverse-alternating sum <= 0. %Y A347442 A273013 counts ordered factorizations of n^2 with alternating product 1. %Y A347442 Cf. A000290, A025047, A330972, A347443, A347449, A347451, A347458, A347459, A347460, A347462. %K A347442 nonn %O A347442 1,4 %A A347442 _Gus Wiseman_, Sep 08 2021 %E A347442 Data section extended up to a(108) by _Antti Karttunen_, Oct 22 2023