A063450 -id:A063450 - cp's OEIS frontend

A063446 Integers m such that d(m+1) = 2*d(m), where d(m) = A000005(m).

1, 5, 7, 13, 37, 39, 49, 55, 61, 65, 69, 73, 77, 87, 129, 134, 157, 183, 185, 193, 194, 221, 237, 247, 249, 254, 265, 275, 277, 295, 309, 313, 321, 327, 343, 363, 365, 397, 398, 417, 421, 437, 454, 455, 457, 458, 469, 471, 473, 475, 482, 493, 497, 505, 517

Offset: 1

Labos Elemer, Jul 24 2001

nonn

			For m = 77, 2*d(77) = 2*4 = 8 = d(78).

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harry J. Smith)

Cf. A000005, A063449, A063450.

Filtered([1..520],n->Tau(n+1)=2*Tau(n)); # Muniru A Asiru, Aug 20 2018

[n: n in [1..600] | NumberOfDivisors(n+1) eq (2* NumberOfDivisors(n))]; // Vincenzo Librandi, Aug 04 2018

Select[Range@ 520, DivisorSigma[0, # + 1] == 2 DivisorSigma[0, #] &] (* Michael De Vlieger, Feb 19 2017 *)

{ n=0; for (m=1, 10^9, if (numdiv(m + 1) == 2*numdiv(m), write("b063446.txt", n++, " ", m); if (n==1000, break)) ) } \\ Harry J. Smith, Aug 21 2009

A063449 Numbers k for which d(k+1) > 2*d(k), where d(j) = A000005(j).

Original entry on oeis.org

11, 17, 19, 23, 29, 31, 35, 41, 43, 47, 53, 59, 67, 71, 79, 83, 89, 95, 97, 101, 103, 107, 109, 111, 113, 119, 125, 127, 131, 137, 139, 143, 149, 151, 155, 159, 161, 163, 167, 169, 173, 179, 181, 191, 197, 199, 203, 209, 211, 215, 219, 223, 227, 229, 233, 239

Offset: 1

Labos Elemer, Jul 24 2001

nonn

d(p+1) >= 2d(p) holds for all primes p and for some composite integers, as well.

			For k = 29: 2*d(29) = 2*2 = 4 < 8 = d(30).
For k = 95: 2*d(95) = 2*4 = 8 < 12 = d(96).

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harry J. Smith)

Cf. A000005, A063446, A063450.

Position[Partition[DivisorSigma[0,Range[250]],2,1],?(2#[[1]]<#[[2]]&),1,Heads->False]//Flatten (* _Harvey P. Dale, Nov 16 2020 *)

is(m) = numdiv(m + 1) > 2*numdiv(m); \\ Harry J. Smith, Aug 21 2009

Edited by Jon E. Schoenfield, Sep 05 2017

A119888 Numbers n such that (n,R_n)>1, where R_n=(10^n -1)/9=A002275(n).

Original entry on oeis.org

3, 6, 9, 12, 15, 18, 21, 22, 24, 27, 30, 33, 36, 39, 42, 44, 45, 48, 51, 54, 57, 60, 63, 66, 69, 72, 75, 78, 81, 84, 87, 88, 90, 93, 96, 99, 102, 105, 108, 110, 111, 114, 117, 120, 123, 126, 129, 132, 134, 135, 138, 141, 144, 150, 153, 154

Offset: 1

Lekraj Beedassy, Aug 04 2006

nonn

Includes all multiples of 3 (A008585) and multiples of 11 with coefficients A063450. A special subsequence is A014950.

Cf. A119905.

cp's OEIS Frontend

A063446 Integers m such that d(m+1) = 2*d(m), where d(m) = A000005(m).

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A063449 Numbers k for which d(k+1) > 2*d(k), where d(j) = A000005(j).

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A119888 Numbers n such that (n,R_n)>1, where R_n=(10^n -1)/9=A002275(n).

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