login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A259541 Numbers n such that antisigma(n) is palindromic. 0
1, 2, 3, 4, 5, 6, 13, 23, 30, 31, 36, 109, 119, 158, 351, 1645, 1653, 2003, 3476, 3520, 3934, 4913, 8037, 9379, 35324, 36516, 91951, 128955, 200003, 390066, 402603, 1068869, 2000003, 2144992, 2467458, 2867828, 3392245, 3607663 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Primes of the form 2*10^k+3 belong the sequence (see A177134 and A081677).

LINKS

Table of n, a(n) for n=1..38.

EXAMPLE

antisigma(1) = 1*2/2 - sigma(1) = 1 - 1 = 0;

antisigma(13) = 13*14/2 - sigma(13) = 91 - 14 = 77;

antisigma(109) = 109*110/2 - sigma(109) = 5995 - 110 = 5885.

MAPLE

with(numtheory): T:=proc(w) local x, y, z; x:=w; y:=0;

for z from 1 to ilog10(x)+1 do y:=10*y+(x mod 10); x:=trunc(x/10);

od; y; end: P:=proc(q) local a, n;

for n from 1 to q do a:=n*(n+1)/2-sigma(n); if a=T(a) then print(n);

fi; od; end: P(10^9);

MATHEMATICA

palQ[n_] := Block[{d = IntegerDigits@ n}, d == Reverse@ d]; Select[Range@ 4000000, palQ[# (# + 1)/2 - DivisorSigma[1, #]] &] (* Michael De Vlieger, Jul 01 2015 *)

PROG

(PARI) isok(n) = my(d = digits(n*(n+1)/2 - sigma(n))); Vecrev(d)==d; \\ Michel Marcus, Jul 01 2015

CROSSREFS

Cf. A024816, A028980, A081677.

Sequence in context: A200330 A121433 A317778 * A274838 A200331 A010349

Adjacent sequences:  A259538 A259539 A259540 * A259542 A259543 A259544

KEYWORD

nonn,base,easy

AUTHOR

Paolo P. Lava, Jun 30 2015

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 19 12:57 EDT 2019. Contains 324222 sequences. (Running on oeis4.)