This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A284202 #18 Jan 13 2025 13:15:09
%S A284202 3,6,10,22,34,142,214,382,862,2302,5182,279934,944782,1572862,1990654,
%T A284202 114791254,127401982,339738622,8153726974,21743271934,4696546738174,
%U A284202 112717121716222,158329674399742,169075682574334,300578991243262
%N A284202 Numbers m such that phi(sum of divisors of m) = lambda(sum of distinct primes dividing m).
%C A284202 Or numbers m such that A000010(A000203(m)) = A002322(A008472(m)), where phi is the Euler totient function and lambda is Carmichael's function.
%C A284202 Properties of the sequence:
%C A284202 (1) for n > 1, it seems that a(n) = 2*A078883(n) = 2*(Lesser member p of a twin prime pair such that p+1 is 3-smooth).
%C A284202 (2) {a(n)} is included in {A282515(n)}.
%C A284202 (3) for n > 2, a(n)/2 is a prime number congruent to 5 mod 6.
%e A284202 34 is in the sequence because A000010(A000203(34)) = A000010(54) = 18, and
%e A284202 A002322(A008472(34)) = A002322(19) = 18.
%t A284202 Select[Range[10^6], EulerPhi@ DivisorSigma[1, #] == CarmichaelLambda[Total@ FactorInteger[#][[All, 1]]] &]
%o A284202 (PARI)
%o A284202 lambda(n) = lcm(znstar(n)[2]); \\ after _Charles R Greathouse IV_ in A002322
%o A284202 sopf(n) = vecsum(factor(n)[,1])
%o A284202 isok(n) = eulerphi(sigma(n)) == lambda(sopf(n)) \\ _Indranil Ghosh_, Mar 22 2017
%Y A284202 Cf. A000010, A000203, A002322, A008472, A078883, A282515.
%K A284202 nonn,more
%O A284202 1,1
%A A284202 _Michel Lagneau_, Mar 22 2017