A391943 Binary widths of the RSA numbers A391940.

330, 364, 397, 426, 430, 463, 496, 512, 530, 563, 576, 596, 629, 640, 663, 696, 704, 729, 762, 768, 768, 795, 829, 862, 895, 896, 928, 962, 995, 1024, 1024, 1028, 1061, 1094, 1128, 1161, 1194, 1227, 1261, 1294, 1327, 1360, 1393, 1427, 1460, 1493, 1526, 1536, 1559, 1593, 1626, 1659, 2048, 2048

Offset

1,1

Comments

From M. F. Hasler, May 21 2026: (Start)

The RSA numbers of the Factoring Challenge in 1991 were labeled according to their number of decimal digits, RSA-100 to RSA-500 and RSA-617. The RSA numbers for the 2001 extension of the challenge were labeled according to the number of binary digits, a(n) = 576, 640, 704, 768, 896, 1024, 1536 and 2048. Of these, only RSA-576 and RSA-640 had been factored when the challenge ended in 2007.

See A391940 for more information about what numbers are listed and in which order.

Duplicate values are a(n) = a(n+1) = 768, 1024 and 2048 for n = 20, 30 and 53. (End)

Links

Table of n, a(n) for n=1..54.

Index entries for sequences related to binary expansion of n.

Formula

a(n) = A070939(A391940(n)).

Prog

(PARI) A391943(n)=exponent(A391940(n))+1 \\ M. F. Hasler, May 21 2026

Crossrefs

Cf. A070939 (bit count), A391940 (RSA numbers).

Cf. also A391944.

Sequence in context: A174848 A300009 A244264 * A117345 A237189 A064262

Adjacent sequences: A391940 A391941 A391942 * A391944 A391945 A391946

Keyword

nonn,base,fini,full

Author

Antti Karttunen, Dec 28 2025

Status

approved