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%I #11 Jul 20 2019 18:25:07
%S 9,21,33,44,57,93,141,169,177,201,213,258,381,393,426,453,501,537,633,
%T 670,678,717,762,921,933,1041,1137,1266,1293,1317,1401,1437,1590,1641,
%U 1686,1713,1761,1821,1857,1893,1941,1990,2181,2217,2361,2433,2509,2517
%N Numbers k such that psigma(k) = psigma(k+1), where psigma(k) = A086469(k).
%C If n =3p and n+1 = 2q where p and q are primes then n is a member.
%H Amiram Eldar, <a href="/A086470/b086470.txt">Table of n, a(n) for n = 1..10000</a>
%e 9 is a member as psigma(9) = 1+3 +9 = psigma(10) = 1+2 +10 = 13.
%t a[n_] := Module[{d = Rest[Divisors[n]]}, 1 + Total@DeleteDuplicatesBy[{#, Sort[FactorInteger[#][[;; , 2]]]} & /@ d, Last][[;; , 1]]]; s={}; a1=0; Do[a2 = a[n]; If[a1 == a2, Append|To[s, n-1]], {n, 1, 2500}]; s (* _Amiram Eldar_, Jul 20 2019 *)
%Y Cf. A086469.
%K nonn
%O 1,1
%A _Amarnath Murthy_, Jul 21 2003
%E Corrected and extended by _David Wasserman_, Mar 07 2005
%E Offset corrected by _Amiram Eldar_, Jul 20 2019
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