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 A062249 a(n) = n + d(n), where d(n) = number of divisors of n, cf. A000005. 14
 2, 4, 5, 7, 7, 10, 9, 12, 12, 14, 13, 18, 15, 18, 19, 21, 19, 24, 21, 26, 25, 26, 25, 32, 28, 30, 31, 34, 31, 38, 33, 38, 37, 38, 39, 45, 39, 42, 43, 48, 43, 50, 45, 50, 51, 50, 49, 58, 52, 56, 55, 58, 55, 62, 59, 64, 61, 62, 61, 72, 63, 66, 69, 71, 69, 74, 69, 74, 73, 78, 73 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Number of cyclic subgroups of dihedral group with 2n elements. a(n) is the n-th smallest number not a divisor of n. - J. Lowell, Apr 06 2008 LINKS Harry J. Smith, Table of n, a(n) for n=1..1000 FORMULA a(n) = n + A000005(n). - Omar E. Pol, Dec 12 2008 From Ilya Gutkovskiy, Apr 12 2017: (Start) G.f.: x/(1 - x)^2 + Sum_{k>=1} x^k/(1 - x^k). Dirichlet g.f.: zeta(s)^2 + zeta(s-1). (End) MAPLE with(numtheory):seq(n+tau(n), n=1..71) ; # Zerinvary Lajos, Jun 04 2008 MATHEMATICA Table[n + DivisorSigma[0, n], {n, 100}] (* Indranil Ghosh, Apr 12 2017 *) PROG (PARI) a(n) = n + numdiv(n) \\ Harry J. Smith, Aug 03 2009 (Haskell) a062249 n = a000005 n + n  -- Reinhard Zumkeller, Mar 29 2014 (Python) from sympy.ntheory import divisor_count [n + divisor_count(n) for n in range(101)] # Indranil Ghosh, Apr 12 2017 CROSSREFS Cf. A007503, A060710, A000005, A049820. Cf. A064491 (iteration, start=1). Sequence in context: A329531 A187325 A112233 * A081404 A255873 A141425 Adjacent sequences:  A062246 A062247 A062248 * A062250 A062251 A062252 KEYWORD nonn AUTHOR Ahmed Fares (ahmedfares(AT)my-deja.com), Jul 01 2001 EXTENSIONS Formula and more terms from Vladeta Jovovic, Jul 03 2001 STATUS approved

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Last modified August 13 00:27 EDT 2020. Contains 336441 sequences. (Running on oeis4.)