A110084
Numbers n with even length such that sigma(n)=d_1^d_2*d_3^d_4 *...*d_(k-1)^d_k where d_1 d_2 ... d_k is the decimal expansion of n.
Original entry on oeis.org
146710, 334552, 12931485, 15734393, 16839254, 20499191, 28661422, 38722820, 43681330, 44463034, 45509442, 55188392, 55938216, 92505149, 1054662422, 1060804965, 1068721252, 1094834272, 1167528360, 1341465139, 1436725284, 1452198772, 1452847236, 1540709585, 1594291529, 1596602643, 1672853710
Offset: 1
45509442 is in the sequence because sigma(55938216)=5^5*9^3*8^2*1^6.
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Do[h = IntegerDigits[n]; k = Length[h]; If[EvenQ[k] && Select[ Range[k/2], h[[2#-1]] == 0 &] == {} && DivisorSigma[1, n]== Product[h[[2j-1]]^h[[2j]], {j, k/2}], Print[n]], {n, 10^8}]
A112010
Numbers m with even length such that phi(m)=phi(d_1^d_2*d_3^d_4*...* d_(k-1)^d_k) where d_1 d_2 ... d_k is the decimal expansion of m.
Original entry on oeis.org
24, 1064, 2592, 6520, 106434, 145166, 237165, 262535, 372780, 491520, 531765, 546410, 566250, 636352, 12716544, 12806910, 13666320, 15116832, 15408692, 17473715, 21645616, 23473515, 23726640, 23728264, 26722436, 26757024, 27933192, 30537364, 30869280, 32118177, 33452293, 34114338, 39602752, 42262365, 44373490
Offset: 1
33452293 is in the sequence because phi(33452293)=phi(3^3*4^5*2^2*9^3).
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Do[h = IntegerDigits[n]; k = Length[h]; If[EvenQ[k] && Select[ Range[k/2], h[[2#-1]] == 0 &] == {} && EulerPhi[n]==EulerPhi [Product[h[[2j-1]]^h[[2j]], {j, k/2}]], Print[n]], {n, 31000000}]
epQ[n_]:=Module[{idn=IntegerDigits[n]},EvenQ[Length[idn]]&& FreeQ[ Take[ idn, {1,-1,2}],0] && EulerPhi[n] == EulerPhi[Times@@(#[[1]]^#[[2]]&/@ Partition[ idn,2])]]; Join[Select[Range[10,99],epQ],Select[Range[ 1000,9999], epQ], Select[Range[100000,999999],epQ], Select[Range[ 10000000, 44999999], epQ]] (* Harvey P. Dale, Feb 24 2016 *)
A112011
Numbers n with even length such that phi(n)=phi(d_1^d_2)*phi(d_3^d_4) *...*phi(d_(k-1)^d_k) where d_1 d_2 ... d_k is the decimal expansion of n.
Original entry on oeis.org
24, 1064, 2592, 6520, 9234, 145166, 245344, 296480, 372780, 491520, 531765, 546410, 566250, 664062, 12806910, 12826710, 14466530, 15408692, 15621268, 17473715, 19946352, 22297520, 23256720, 30537364, 30869280, 32118177
Offset: 1
39602752 is in the sequence because phi(39602752)=
phi(3^9)*phi(6^0)*phi(2^7)*phi(5^2).
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Do[h = IntegerDigits[n]; k = Length[h]; If[EvenQ[k] && Select[ Range[k/2], h[[2#-1]] == 0 &] == {} && EulerPhi[n]== Product[EulerPhi[h[[2j-1]]^h[[2j]]], {j, k/2}], Print[n]], {n, 35000000}]
Showing 1-3 of 3 results.
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