cp's OEIS Frontend

A377455 Numbers k such that k and k+1 are both terms in A377385.

%I A377455 #8 Oct 29 2024 12:33:00
%S A377455 1,1224,126191,428519,649727,1015416,1988064,3425856,4542740,4574240,
%T A377455 4743900,4813668,5131008,6899840,7001315,7172424,7356096,8020583,
%U A377455 10206000,11146421,11566800,11597999,11693807,12556700,13742624,13745759,13831487,14365120,16939799,20561400
%N A377455 Numbers k such that k and k+1 are both terms in A377385.
%H A377455 Amiram Eldar, <a href="/A377455/b377455.txt">Table of n, a(n) for n = 1..10000</a>
%e A377455 1224 is a term since both 1224 and 1225 are in A377385: 1224/A034968(1224) = 204 and 204/A034968(204) = 34 are integers, and 1225/A034968(1225) = 175 and 175/A034968(175) = 35 are integers.
%t A377455 fdigsum[n_] := Module[{k = n, m = 2, r, s = 0}, While[{k, r} = QuotientRemainder[k, m]; k != 0 || r != 0, s += r; m++]; s]; q[k_] := q[k] = Module[{f = fdigsum[k]}, Divisible[k, f] && Divisible[k/f, fdigsum[k/f]]]; Select[Range[2*10^6], q[#] && q[#+1] &]
%o A377455 (PARI) fdigsum(n) = {my(k = n, m = 2, r, s = 0); while([k, r] = divrem(k, m); k != 0 || r != 0, s += r; m++); s;}
%o A377455 is1(k) = {my(f = fdigsum(k)); !(k % f) && !((k/f) % fdigsum(k/f));}
%o A377455 lista(kmax) = {my(q1 = is1(1), q2); for(k = 2, kmax, q2 = is1(k); if(q1 && q2, print1(k-1, ", ")); q1 = q2);}
%Y A377455 Cf. A034968.
%Y A377455 Subsequence of A118363, A328205 and A377385.
%Y A377455 Subsequences: A377456, A377457.
%Y A377455 Analogous sequences: A376793 (binary), A377271 (Zeckendorf).
%K A377455 nonn,base
%O A377455 1,2
%A A377455 _Amiram Eldar_, Oct 29 2024