The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A085981 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A085981

Number of 7's in decimal expansion of prime(n).
(history; published version)

#12 by Michael De Vlieger at Mon Oct 30 09:52:24 EDT 2023

STATUS

reviewed

approved

#11 by Michael De Vlieger at Mon Oct 30 09:52:22 EDT 2023

STATUS

proposed

reviewed

#10 by Paolo Xausa at Mon Oct 30 06:00:55 EDT 2023

STATUS

editing

proposed

#9 by Paolo Xausa at Mon Oct 30 05:59:25 EDT 2023

MATHEMATICA

DigitCount[Prime[Range[100]], 10, 7] (* Paolo Xausa, Oct 30 2023 *)

STATUS

approved

editing

#8 by N. J. A. Sloane at Fri Dec 15 17:36:31 EST 2017

AUTHOR

_Jason Earls (zevi_35711(AT)yahoo.com), _, Jul 06 2003

Discussion

Fri Dec 15

17:36

OEIS Server: https://oeis.org/edit/global/2722

#7 by Reinhard Zumkeller at Wed Apr 09 10:20:28 EDT 2014

STATUS

editing

approved

#6 by Reinhard Zumkeller at Tue Apr 08 16:42:50 EDT 2014

PROG

(Haskell)

a085981 = count7 0 . a000040 where

count7 c x | d == 7 = if x < 10 then c + 1 else count7 (c + 1) x'

| otherwise = if x < 10 then c else count7 c x'

where (x', d) = divMod x 10

-- Reinhard Zumkeller, Apr 08 2014

#5 by Reinhard Zumkeller at Tue Apr 08 16:42:24 EDT 2014

LINKS

Reinhard Zumkeller, <a href="/A085981/b085981.txt">Table of n, a(n) for n = 1..10000</a>

STATUS

approved

editing

#4 by N. J. A. Sloane at Fri Jan 09 03:00:00 EST 2009

KEYWORD

base,nonn,new

AUTHOR

Jason Earls (jcearlszevi_35711(AT)cableoneyahoo.netcom), Jul 06 2003

#3 by N. J. A. Sloane at Wed Sep 22 03:00:00 EDT 2004

KEYWORD

base,nonn,new

AUTHOR

Jason Earls (jcearls(AT)4grccableone.comnet), Jul 06 2003