A138125 Final digit of n-th even superperfect number A061652(n).

2, 4, 6, 4, 6, 6, 4, 4, 6, 6, 4, 4, 6, 4, 4, 4, 6, 6, 6, 4, 6, 6, 6, 6, 6, 6, 6, 4, 4, 6, 4, 4, 6, 4, 6, 6, 6, 6, 6, 4, 4, 4, 6, 6, 4, 6, 6

Offset

1,1

Comments

Also, final digit of n-th superperfect number A019279(n), if there are no odd superperfect numbers.

Links

Table of n, a(n) for n=1..47.

Landon Curt Noll, Mersenne Prime Digits.

Formula

a(1)=2. For n>1, if final digit of n-th Mersenne prime A000668(n) is equal to 1 then a(n)=6, otherwise a(n)=4.

Example

a(5)=6 because the 5th even superperfect number A061652(5) is 4096 and the final digit of 4096 is 6.
a(34)=4 because the final digit of 34th Mersenne prime is 7. a(39)=6 because the final digit of 39th Mersenne prime is 1.
.............................................................
............... SHORT TABLE OF FINAL DIGITS .................
.............................................................
Final digit of ..... Final digit of Even ..... Final digit of
Mersenne prime ..... Superperfect number ..... Perfect number
A000668 ............ A061652 ................. A000396........
(3) ................ (2) ..................... (6) ........... (For n=1, only)
(7) ................ (4) ..................... (8) ...........
(1) ................ (6) ..................... (6) ...........

Mathematica

Mod[#, 10]&/@(2^(MersennePrimeExponent[Range[47]]-1)) (* Harvey P. Dale, Feb 23 2023 *)

Crossrefs

Cf. A000030, A000396, A000668, A077648, A019279, A061652, A135613, A135617, A138125.

Sequence in context: A018841 A182043 A337937 * A098793 A083220 A085896

Adjacent sequences: A138122 A138123 A138124 * A138126 A138127 A138128

Keyword

base,nonn,less

Author

Omar E. Pol, Apr 01 2008, corrected Apr 03 2008

Extensions

a(40)-a(47) from Jinyuan Wang, Mar 14 2020

Status

approved