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 A326122 a(n) = 10 * sigma(n). 2
 10, 30, 40, 70, 60, 120, 80, 150, 130, 180, 120, 280, 140, 240, 240, 310, 180, 390, 200, 420, 320, 360, 240, 600, 310, 420, 400, 560, 300, 720, 320, 630, 480, 540, 480, 910, 380, 600, 560, 900, 420, 960, 440, 840, 780, 720, 480, 1240, 570, 930, 720, 980, 540, 1200, 720, 1200, 800, 900, 600, 1680, 620, 960 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 10 times the sum of the divisors of n. a(n) is also the total number of horizontal rhombuses in the terraces of the n-th level of an irregular step pyramid (starting from the top) where the structure of every 36-degree-three-dimensional sector arises after the 36-degree-zig-zag folding of every row of the diagram of the isosceles triangle A237593. The top of the pyramid is a 10-pointed star formed by 10 rhombuses (see Links section). LINKS FORMULA a(n) = 10*A000203(n) = 5*A074400(n) = 2*A274535(n). a(n) = A000203(n) + A325299(n) = A074400(n) + A319528(n). Dirichlet g.f.: 10*zeta(s-1)*zeta(s). - (After Ilya Gutkovskiy) MAPLE with(numtheory): seq(10*sigma(n), n=1..64); MATHEMATICA 10*DivisorSigma[1, Range[70]] (* After Harvey P. Dale *) PROG (PARI) a(n) = 10 * sigma(n); (GAP) List([1..70], n->10*Sigma(n)); # After Muniru A Asiru (MAGMA) [10*DivisorSigma(1, n): n in [1..70]]; // Vincenzo Librandi, Jul 26 2019 CROSSREFS k times sigma(n), k=1..9: A000203, A074400, A272027, A239050, A274535, A274536, A319527, A319528, A325299. Cf. A008592, A033583, A124080, A124252, A142342, A153780, A237593. Sequence in context: A031195 A034117 A104863 * A027183 A333300 A096844 Adjacent sequences:  A326119 A326120 A326121 * A326123 A326124 A326125 KEYWORD nonn,easy AUTHOR Omar E. Pol, Jul 13 2019 STATUS approved

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Last modified September 28 22:03 EDT 2020. Contains 337417 sequences. (Running on oeis4.)