The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A238971 The number of nodes at odd level in divisor lattice in canonical order. 3
 0, 1, 1, 2, 2, 3, 4, 2, 4, 4, 6, 8, 3, 5, 6, 8, 9, 12, 16, 3, 6, 7, 10, 8, 12, 16, 13, 18, 24, 32, 4, 7, 9, 12, 10, 15, 20, 16, 18, 24, 32, 27, 36, 48, 64, 4, 8, 10, 14, 12, 18, 24, 12, 20, 22, 30, 40, 24, 32, 36, 48, 64, 40, 54, 72, 96, 128 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS Andrew Howroyd, Table of n, a(n) for n = 0..2713 (rows 0..20) S.-H. Cha, E. G. DuCasse, and L. V. Quintas, Graph Invariants Based on the Divides Relation and Ordered by Prime Signatures, arxiv:1405.5283 [math.NT], 2014. FORMULA From Andrew Howroyd, Mar 25 2020: (Start) T(n,k) = A056924(A063008(n,k)). T(n,k) = A238963(n,k) - A238970(n,k). T(n,k) = floor(A238963(n,k)/2). (End) EXAMPLE Triangle T(n,k) begins:   0;   1;   1, 2;   2, 3, 4;   2, 4, 4,  6, 8;   3, 5, 6,  8, 9, 12, 16;   3, 6, 7, 10, 8, 12, 16, 13, 18, 24, 32;   ... MAPLE b:= (n, i)-> `if`(n=0 or i=1, [[1\$n]], [map(x->     [i, x[]], b(n-i, min(n-i, i)))[], b(n, i-1)[]]): T:= n-> map(x-> floor(numtheory[tau](mul(ithprime(i)         ^x[i], i=1..nops(x)))/2), b(n\$2))[]: seq(T(n), n=0..9);  # Alois P. Heinz, Mar 25 2020 PROG (PARI) b(n)={numdiv(n)\2} N(sig)={prod(k=1, #sig, prime(k)^sig[k])} Row(n)={apply(s->b(N(s)), vecsort([Vecrev(p) | p<-partitions(n)], , 4))} { for(n=0, 8, print(Row(n))) } \\ Andrew Howroyd, Mar 25 2020 CROSSREFS Cf. A238958 in canonical order. Cf. A056924, A063008, A238963, A238970. Sequence in context: A114892 A285705 A238958 * A194331 A290600 A143595 Adjacent sequences:  A238968 A238969 A238970 * A238972 A238973 A238974 KEYWORD nonn,tabf AUTHOR Sung-Hyuk Cha, Mar 07 2014 EXTENSIONS Offset changed and terms a(50) and beyond from Andrew Howroyd, Mar 25 2020 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 June 21 07:27 EDT 2021. Contains 345358 sequences. (Running on oeis4.)