This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A135617 a(n) is the initial digit of n-th even perfect number. 7
 6, 2, 4, 8, 3, 8, 1, 2, 2, 1, 1, 1, 2, 1, 5, 1, 9, 3, 1, 4, 1, 5, 3, 9, 1, 8, 3, 1, 1, 1, 2, 1, 8, 8, 3, 1, 8, 9, 4, 7, 4, 7, 4, 7, 2, 1, 5 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(n) is also the initial digit of n-th perfect number A000396(n) if there are no odd perfect numbers. LINKS Omar E. Pol, Los nĂºmeros perfectos, (in Spanish). EXAMPLE a(5) = 3 because the 5th even perfect number is 33550336 and the initial digit of 33550336 is 3. MATHEMATICA lst = {* the list of terms in A000043 *}; f[n_] := Block[{pn = (2^n - 1) (2^(n - 1))}, Quotient[pn, 10^Floor[ Log[10, pn]] ]]; f@# & /@ lst - Robert G. Wilson v, Apr 01 2008 CROSSREFS Cf. A000030, A000396, A077648, A094540, A133033. Sequence in context: A020831 A298777 A156590 * A019930 A169843 A123139 Adjacent sequences:  A135614 A135615 A135616 * A135618 A135619 A135620 KEYWORD nonn,base,more AUTHOR Omar E. Pol, Mar 01 2008 EXTENSIONS More terms from Robert G. Wilson v, Apr 01 2008 Definition clarified by Omar E. Pol, Apr 14 2018 a(40)-a(47) from Ivan Panchenko, Apr 16 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified March 18 16:00 EDT 2019. Contains 321292 sequences. (Running on oeis4.)