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 A321440 Number of partitions of n into consecutive parts, all singletons except the largest. 4
 1, 1, 2, 3, 3, 4, 5, 4, 5, 7, 5, 6, 8, 5, 8, 10, 5, 8, 10, 7, 10, 11, 7, 8, 13, 9, 9, 14, 7, 12, 15, 6, 12, 13, 11, 15, 14, 8, 10, 19, 10, 12, 18, 8, 16, 19, 9, 12, 17, 14, 16, 16, 10, 15, 21, 15, 14, 20, 7, 16, 25, 7, 20, 21, 14, 18, 18, 14, 12, 26, 16, 17 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Number of representations of n as the difference of two distinct triangular numbers, plus any multiple of the order of the larger triangular number. LINKS Chai Wah Wu, Table of n, a(n) for n = 0..10000 Dandan Chen and Rong Chen, Generating Functions of the Hurwitz Class Numbers Associated with Certain Mock Theta Functions, arXiv:2107.04809 [math.NT], 2021. N. J. A. Sloane, Coordination Sequences, Planing Numbers, and Other Recent Sequences (II), Experimental Mathematics Seminar, Rutgers University, Jan 31 2019, Part I, Part 2, Slides. (Mentions this sequence) EXAMPLE Here are the derivations of the terms given. Partitions are listed as strings of digits. n = 0: (empty partition) n = 1: 1 n = 2: 11, 2 n = 3: 111, 12, 3 n = 4: 1111, 22, 4 n = 5: 11111, 122, 23, 5 n = 6: 111111, 123, 222, 33, 6 n = 7: 1111111, 1222, 34, 7 n = 8: 11111111, 2222, 233, 44, 8 n = 9: 111111111, 12222, 1233, 234, 333, 45, 9 n = 10: 1111111111, 1234, 22222, 55, (10) PROG (Python) from sympy.utilities.iterables import partitions def A321440(n):     return 1 if n == 0 else sum(1 for s, p in partitions(n, size=True) if len(p)-1 == max(p)-min(p) == s-p[max(p)]) # Chai Wah Wu, Nov 09 2018 from __future__ import division def A321440(n): # a faster program based on the characterization in the comments     if n == 0:         return 1     c = 0     for i in range(n):         mi = i*(i+1)//2 + n         for j in range(i+1, n+1):             k = mi - j*(j+1)//2             if k < 0:                 break             if not k % j:                 c += 1     return c # Chai Wah Wu, Nov 09 2018 CROSSREFS See comment by Emeric Deutsch at A001227 (partitions into consecutive parts, all singletons); the partitions considered in the present sequence are a superset of those described by Deutsch. Cf. A321441, A321443. Sequence in context: A341511 A089308 A305579 * A115729 A115728 A188553 Adjacent sequences:  A321437 A321438 A321439 * A321441 A321442 A321443 KEYWORD nonn AUTHOR Allan C. Wechsler, Nov 09 2018 EXTENSIONS More terms from Chai Wah Wu, Nov 09 2018 STATUS approved

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Last modified September 25 19:04 EDT 2021. Contains 347659 sequences. (Running on oeis4.)