A126169 -id:A126169 - cp's OEIS frontend

A126171 Number of infinitary amicable pairs (i,j) with i

0, 0, 2, 6, 22, 62, 189, 444, 1116, 2594, 6051, 14141

Offset: 1

Ant King, Dec 22 2006

A divisor of n is called infinitary if it is a product of divisors of the form p^{y_a 2^a}, where p^y is a prime power dividing n and sum_a y_a 2^a is the binary representation of y.

			a(6)=62 because there are 62 infinitary amicable pairs (m,n) with m<n and m<=10^6

Pedersen J. M., Known amicable pairs.

Cf. A126169, A049417, A126168, A037445, A126170.

ExponentList[n_Integer, factors_List] := {#, IntegerExponent[n, # ]} & /@ factors; InfinitaryDivisors[1] := {1}; InfinitaryDivisors[n_Integer?Positive] := Module[ { factors = First /@ FactorInteger[n], d = Divisors[n] }, d[[Flatten[Position[ Transpose[ Thread[Function[{f, g}, BitOr[f, g] == g][ #, Last[ # ]]] & /@ Transpose[Last /@ ExponentList[ #, factors] & /@ d]], ?( And @@ # &), {1}]] ]] ] Null; properinfinitarydivisorsum[k] := Plus @@ InfinitaryDivisors[k] - k; InfinitaryAmicableNumberQ[k_] := If[Nest[properinfinitarydivisorsum, k, 2] == k && ! properinfinitarydivisorsum[k] == k, True, False]; data1 = Select[ Range[10^6], InfinitaryAmicableNumberQ[ # ] &]; data2 = properinfinitarydivisorsum[ # ] & /@ data1; data3 = Table[{data1[[k]], data2[[k]]}, {k, 1, Length[data1]}]; data4 = Select[data3, First[ # ] < Last[ # ] &]; Table[Length[Select[data4, First[ # ] < 10^k &]], {k, 1, 6}]

Infinitary amicable pairs (m,n) satisfy isigma(m)=isigma(n)=m+n, with m

A126173 Larger element of a reduced infinitary amicable pair.

Original entry on oeis.org

2295, 75495, 817479, 1902215, 1341495, 1348935, 2226014, 2421704, 3123735, 3010215, 5644415, 4282215, 7509159, 10106504, 12900734, 24519159, 31356314, 41950359, 43321095, 80870615, 42125144, 85141719, 87689415, 87802407, 86477895, 105993657, 168669879, 129081735

Offset: 1

Ant King, Dec 23 2006

nonn

A divisor of n is called infinitary if it is a product of divisors of the form p^{y_a 2^a}, where p^y is a prime power dividing n and sum_a y_a 2^a is the binary representation of y.

			a(3)=817479 because 817479 is the largest member of the third reduced infinitary amicable pair, (573560,817479)

Amiram Eldar, Table of n, a(n) for n = 1..278
Jan Munch Pedersen, Tables of Aliquot Cycles.

Cf. A126169, A049417, A126168, A037445, A126170, A126171, A126172, A126174, A126175, A126176.

ExponentList[n_Integer, factors_List] := {#, IntegerExponent[n, # ]} & /@ factors; InfinitaryDivisors[1] := {1}; InfinitaryDivisors[n_Integer?Positive] := Module[ { factors = First /@ FactorInteger[n], d = Divisors[n] }, d[[Flatten[Position[ Transpose[ Thread[Function[{f, g}, BitOr[f, g] == g][ #, Last[ # ]]] & /@ Transpose[Last /@ ExponentList[ #, factors] & /@ d]], ?( And @@ # &), {1}]] ]] ] Null; properinfinitarydivisorsum[k] := Plus @@ InfinitaryDivisors[k] - k; ReducedInfinitaryAmicableNumberQ[n_] := If[properinfinitarydivisorsum[properinfinitarydivisorsum[ n] - 1] == n + 1 && n > 1, True, False]; ReducedInfinitaryAmicablePairList[k_] := (anlist = Select[Range[k], ReducedInfinitaryAmicableNumberQ[ # ] &]; prlist = Table[Sort[{anlist[[n]], properinfinitarydivisorsum[anlist[[n]]] - 1}], {n, 1, Length[anlist]}]; amprlist = Union[prlist, prlist]); data1 = ReducedInfinitaryAmicablePairList[10^7]; Table[Last[data1[[k]]], {k, 1, Length[data1]}]
fun[p_, e_] := Module[{b = IntegerDigits[e, 2]}, m = Length[b]; Product[If[b[[j]] > 0, 1 + p^(2^(m - j)), 1], {j, 1, m}]]; infs[n_] := Times @@ (fun @@@ FactorInteger[n]) - n; s = {}; Do[k = infs[n] - 1; If[k > n && infs[k] == n + 1, AppendTo[s, k]], {n, 2, 10^5}]; s (* Amiram Eldar, Jan 22 2019 *)

The values of n for which isigma(m)=isigma(n)=m+n+1, where n>m and isigma(n) is given by A049417(n).

a(15)-a(28) from Amiram Eldar, Jan 22 2019

A126174 Smaller member of an augmented infinitary amicable pair.

Original entry on oeis.org

1252216, 1754536, 2166136, 2362360, 6224890, 7626136, 7851256, 9581320, 12480160, 12494856, 13324311, 15218560, 15422536, 19028296, 29180466, 36716680, 37542190, 40682824, 45131416, 45495352, 56523810, 67195305, 71570296, 80524665, 89740456, 93182440, 101304490

Offset: 1

Ant King, Dec 23 2006

A divisor of n is called infinitary if it is a product of divisors of the form p^{y_a 2^a}, where p^y is a prime power dividing n and sum_a y_a 2^a is the binary representation of y.

			a(3)=2166136 because 2166136 is the smaller element of the third augmented infinitary amicable pair, (2166136,2580105).

Amiram Eldar, Table of n, a(n) for n = 1..276
Jan Munch Pedersen, Tables of Aliquot Cycles.

Cf. A126169, A049417, A126168, A037445, A126170, A126171, A126173, A126175, A126176.

ExponentList[n_Integer, factors_List] := {#, IntegerExponent[n, # ]} & /@ factors; InfinitaryDivisors[1] := {1}; InfinitaryDivisors[n_Integer?Positive] := Module[ { factors = First /@ FactorInteger[n], d = Divisors[n] }, d[[Flatten[Position[ Transpose[ Thread[Function[{f, g}, BitOr[f, g] == g][ #, Last[ # ]]] & /@ Transpose[Last /@ ExponentList[ #, factors] & /@ d]], ?( And @@ # &), {1}]] ]] ] Null; properinfinitarydivisorsum[k] := Plus @@ InfinitaryDivisors[k] - k; AugmentedInfinitaryAmicableNumberQ[n_] := If[properinfinitarydivisorsum[properinfinitarydivisorsum[ n] + 1] == n - 1 && ! properinfinitarydivisorsum[n] + 1 == n, True, False]; AugmentedInfinitaryAmicablePairList[k_] := (anlist = Select[Range[k], AugmentedInfinitaryAmicableNumberQ[ # ] &]; prlist = Table[ Sort[{anlist[[n]], properinfinitarydivisorsum[anlist[[n]]] + 1}], {n, 1, Length[anlist]}]; amprlist = Union[prlist, prlist]); data = AugmentedInfinitaryAmicablePairList[10^7]; Table[First[data[[k]]], {k, 1, Length[data]}]
fun[p_, e_] := Module[{b = IntegerDigits[e, 2]}, m = Length[b]; Product[If[b[[j]] > 0, 1 + p^(2^(m - j)), 1], {j, 1, m}]]; infs[n_] := Times @@ (fun @@@ FactorInteger[n]) - n; s = {}; Do[k = infs[n] + 1; If[k > n && infs[k] == n - 1, AppendTo[s, n]], {n, 2, 10^9}]; s (* Amiram Eldar, Jan 20 2019 *)

The values of m for which isigma(m)=isigma(n)=m+n-1, where mA049417(n).

a(9)-a(27) from Amiram Eldar, Jan 20 2019

A126175 Larger member of an augmented infinitary amicable pair.

Original entry on oeis.org

1483785, 2479065, 2580105, 4895241, 7336455, 9100905, 10350345, 16367481, 17307105, 24829945, 15706090, 27866241, 15439545, 23872185, 53763535, 63075321, 41337555, 60923577, 51394665, 56802249, 110691295, 73809496, 89870985, 82771336, 92586585, 150672921, 108212055

Offset: 1

Ant King, Dec 23 2006

A divisor of n is called infinitary if it is a product of divisors of the form p^{y_a 2^a}, where p^y is a prime power dividing n and sum_a y_a 2^a is the binary representation of y.

			a(3)=2580105 because 2580105 is the larger member of the third augmented infinitary amicable pair, (2166136,2580105).

Amiram Eldar, Table of n, a(n) for n = 1..276
Jan Munch Pedersen, Tables of Aliquot Cycles.

Cf. A126169, A049417, A126168, A037445, A126170, A126171, A126173, A126174, A126176.

ExponentList[n_Integer, factors_List] := {#, IntegerExponent[n, # ]} & /@ factors; InfinitaryDivisors[1] := {1}; InfinitaryDivisors[n_Integer?Positive] := Module[ { factors = First /@ FactorInteger[n], d = Divisors[n] }, d[[Flatten[Position[ Transpose[ Thread[Function[{f, g}, BitOr[f, g] == g][ #, Last[ # ]]] & /@ Transpose[Last /@ ExponentList[ #, factors] & /@ d]], ?( And @@ # &), {1}]] ]] ] Null; properinfinitarydivisorsum[k] := Plus @@ InfinitaryDivisors[k] - k; AugmentedInfinitaryAmicableNumberQ[n_] := If[properinfinitarydivisorsum[properinfinitarydivisorsum[ n] + 1] == n - 1 && ! properinfinitarydivisorsum[n] + 1 == n, True, False]; AugmentedInfinitaryAmicablePairList[k_] := (anlist = Select[Range[k], AugmentedInfinitaryAmicableNumberQ[ # ] &]; prlist = Table[ Sort[{anlist[[n]], properinfinitarydivisorsum[anlist[[n]]] + 1}], {n, 1, Length[anlist]}]; amprlist = Union[prlist, prlist]); data = AugmentedInfinitaryAmicablePairList[10^7]; Table[Last[data[[k]]], {k, 1, Length[data]}]
fun[p_, e_] := Module[{b = IntegerDigits[e, 2]}, m = Length[b]; Product[If[b[[j]] > 0, 1 + p^(2^(m - j)), 1], {j, 1, m}]]; infs[n_] := Times @@ (fun @@@ FactorInteger[n]) - n; s = {}; Do[k = infs[n] + 1; If[k > n && infs[k] == n - 1, AppendTo[s, k]], {n, 2, 10^9}]; s (* Amiram Eldar, Jan 20 2019 *)

The values of n for which isigma(m)=isigma(n)=m+n-1, where n>m and isigma(n) is given by A049417(n).

a(9)-a(27) from Amiram Eldar, Jan 20 2019

A126172 Smaller element of a reduced infinitary amicable pair.

Original entry on oeis.org

2024, 62744, 573560, 1000824, 1173704, 1208504, 1921185, 2140215, 2198504, 2312024, 2580864, 4012184, 5416280, 9247095, 12500865, 13496840, 23939685, 26409320, 34093304, 37324584, 40818855, 52026920, 66275384, 76011992, 79842104, 101366342, 101589320, 106004024

Offset: 1

Ant King, Dec 23 2006

nonn

A divisor of n is called infinitary if it is a product of divisors of the form p^{y_a 2^a}, where p^y is a prime power dividing n and sum_a y_a 2^a is the binary representation of y.

			a(3)=573560 because 573560 is the smaller element of the third reduced infinitary amicable pair, (573560, 817479)

Amiram Eldar, Table of n, a(n) for n = 1..278
Jan Munch Pedersen, Tables of Aliquot Cycles.

Cf. A126169, A049417, A126168, A037445, A126170, A126171, A126173, A126174, A126175, A126176.

ExponentList[n_Integer, factors_List] := {#, IntegerExponent[n, # ]} & /@ factors; InfinitaryDivisors[1] := {1}; InfinitaryDivisors[n_Integer?Positive] := Module[ { factors = First /@ FactorInteger[n], d = Divisors[n] }, d[[Flatten[Position[ Transpose[ Thread[Function[{f, g}, BitOr[f, g] == g][ #, Last[ # ]]] & /@ Transpose[Last /@ ExponentList[ #, factors] & /@ d]], ?( And @@ # &), {1}]] ]] ] Null; properinfinitarydivisorsum[k] := Plus @@ InfinitaryDivisors[k] - k; ReducedInfinitaryAmicableNumberQ[n_] := If[properinfinitarydivisorsum[properinfinitarydivisorsum[ n] - 1] == n + 1 && n > 1, True, False]; ReducedInfinitaryAmicablePairList[k_] := (anlist = Select[Range[k], ReducedInfinitaryAmicableNumberQ[ # ] &]; prlist = Table[Sort[{anlist[[n]], properinfinitarydivisorsum[anlist[[n]]] - 1}], {n, 1, Length[anlist]}]; amprlist = Union[prlist, prlist]); data1 = ReducedInfinitaryAmicablePairList[ 10^7]; Table[First[data1[[k]]], {k, 1, Length[data1]}]
fun[p_, e_] := Module[{b = IntegerDigits[e, 2]}, m = Length[b]; Product[If[b[[j]] > 0, 1 + p^(2^(m - j)), 1], {j, 1, m}]]; infs[n_] := Times @@ (fun @@@ FactorInteger[n]) - n; s = {}; Do[k = infs[n] - 1; If[k > n && infs[k] == n + 1, AppendTo[s, n]], {n, 2, 10^5}]; s (* Amiram Eldar, Jan 22 2019 *)

The values of m for which isigma(m)=isigma(n)=m+n+1, where mA049417(n).

a(15)-a(28) from Amiram Eldar, Jan 22 2019

A126176 Number of augmented infinitary amicable pairs (i,j) with i

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 8, 26, 48, 104, 227

Offset: 1

Ant King, Dec 24 2006

A divisor of n is called infinitary if it is a product of divisors of the form p^{y_a 2^a}, where p^y is a prime power dividing n and sum_a y_a 2^a is the binary representation of y.

			a(9)=48 because there are 48 augmented infinitary amicable pairs (m,n) with m<n and m<=10^9

Pedersen J. M., Known amicable pairs.

Cf. A126169, A049417, A126168, A037445, A126170, A126171, A126172, A126173, A126174, A126175.

ExponentList[n_Integer, factors_List] := {#, IntegerExponent[n, # ]} & /@ factors; InfinitaryDivisors[1] := {1}; InfinitaryDivisors[n_Integer?Positive] := Module[ { factors = First /@ FactorInteger[n], d = Divisors[n] }, d[[Flatten[Position[ Transpose[ Thread[Function[{f, g}, BitOr[f, g] == g][ #, Last[ # ]]] & /@ Transpose[Last /@ ExponentList[ #, factors] & /@ d]], ?( And @@ # &), {1}]] ]] ] Null; properinfinitarydivisorsum[k] := Plus @@ InfinitaryDivisors[k] - k; AugmentedInfinitaryAmicableNumberQ[n_] := If[properinfinitarydivisorsum[properinfinitarydivisorsum[ n] + 1] == n - 1 && ! properinfinitarydivisorsum[n] + 1 == n, True, False]; AugmentedInfinitaryAmicablePairList[k_] := (anlist = Select[Range[k], AugmentedInfinitaryAmicableNumberQ[ # ] &]; prlist = Table[ Sort[{anlist[[n]], properinfinitarydivisorsum[anlist[[n]]] + 1}], {n, 1, Length[anlist]}]; amprlist = Union[prlist, prlist]); data = AugmentedInfinitaryAmicablePairList[10^7]; Table[Length[Select[data, First[ # ] < 10^k &]], {k, 1, 7}]

augmented infinitary amicable pairs (m,n) satisfy isigma(m)=isigma(n)=m+n-1, with m

A348343 Smaller member of a noninfinitary amicable pair: numbers (k, m) such that nisigma(k) = m and nisigma(m) = k, where nisigma(k) is the sum of the noninfinitary divisors of k (A348271).

Original entry on oeis.org

336, 1792, 5376, 6096, 21504, 32004, 97536, 34062336, 64512000, 118008576, 30064771072

Offset: 1

Amiram Eldar, Oct 13 2021

The larger counterparts are in A348344.

			336 is a term since A348271(336) = 448 and A348271(448) = 336.

Cf. A327633, A348271, A348344.

Similar sequences: A002025, A002952, A126165, A126169, A259038, A292980, A322541, A324708.

f[p_, e_] := Module[{b = IntegerDigits[e, 2], m}, m = Length[b]; Product[If[b[[j]] > 0, 1 + p^(2^(m - j)), 1], {j, 1, m}]]; isigma[1] = 1; isigma[n_] := Times @@ f @@@ FactorInteger[n]; s[n_] := DivisorSigma[1,n] - isigma[n]; seq={}; Do[m=s[n]; If[m>n && s[m]==n, AppendTo[seq, n]], {n,1,10^4}]; seq

A004607 Infinitary sociable numbers (smallest member of cycle).

Original entry on oeis.org

1026, 10098, 10260, 12420, 41800, 45696, 100980, 241824, 448800, 512946, 685440, 830568, 4938136, 6732000, 9424800, 12647808, 13959680, 14958944, 17878998, 25581600, 28158165, 32440716, 36072320, 55204500, 74062944

Offset: 1

N. J. A. Sloane

If n = Product p_i^a_i, d = Product p_i^c_i is an infinitary divisor of n if each c_i has a zero bit in its binary representation everywhere that the corresponding a_i does.
From Amiram Eldar, Mar 25 2023: (Start)
Analogous to A003416 with the sum of the aliquot infinitary divisors function (A126168) instead of A001065.
Only cycles of length greater than 2 are here. Cycles of length 1 correspond to infinitary perfect numbers (A007357), and cycles of length 2 correspond to infinitary amicable pairs (A126169 and A126170).
The corresponding cycles are of lengths 4, 4, 4, 6, 4, 4, 4, 4, 11, 6, 4, 6, 4, 11, 6, 23, 4, 4, 85, 4, 4, 4, 4, 4, 4, ...
It is conjectured that there are no missing terms in the data, but it was not proven. For example, it is not known that the infinitary aliquot sequence that starts at 840 does not reach 840 again (see A361421). (End)

Graeme L. Cohen, On an integer's infinitary divisors, Math. Comp. 54 (189) (1990) 395-411.
J. O. M. Pedersen, Tables of Aliquot Cycles.
J. O. M. Pedersen, Tables of Aliquot Cycles. [Via Internet Archive Wayback-Machine]
J. O. M. Pedersen, Tables of Aliquot Cycles. [Cached copy, pdf file only]

Cf. A001065, A003416, A007357, A126168, A126169, A126170, A361421.

Showing 1-10 of 18 results. Next

cp's OEIS Frontend

A126170 Larger member of an infinitary amicable pair.

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A324708 Lesser of tri-unitary amicable numbers pair: numbers (m, n) such that tsigma(m) = tsigma(n) = m + n, where tsigma(n) is the sum of the tri-unitary divisors of n (A324706).

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A126171 Number of infinitary amicable pairs (i,j) with i

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A126173 Larger element of a reduced infinitary amicable pair.

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A126174 Smaller member of an augmented infinitary amicable pair.

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A126175 Larger member of an augmented infinitary amicable pair.

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A126172 Smaller element of a reduced infinitary amicable pair.

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