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A230820 Table, read by antidiagonals, of palindromic primes in base b expressed in decimal. 2
3, 2, 5, 2, 13, 7, 2, 3, 23, 17, 2, 3, 5, 151, 31, 2, 3, 31, 17, 173, 73, 2, 3, 5, 41, 29, 233, 107, 2, 3, 5, 7, 67, 59, 757, 127, 2, 3, 5, 71, 37, 83, 257, 937, 257, 2, 3, 5, 7, 107, 43, 109, 373, 1093, 313, 2, 3, 5, 7, 73, 157, 61, 701, 409, 1249, 443 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..66.

EXAMPLE

\r

b\

.2.3...5...7...17...31...73..107..127...257...313...443..1193..1453..1571.=A016041

.3.2..13..23..151..173..233..757..937..1093..1249..1429..1487..1667..1733.=A029971

.4.2...3...5...17...29...59..257..373...409...461...509...787...839...887.=A029972

.5.2...3..31...41...67...83..109..701...911..1091..1171..1277..1327..1667.=A029973

.6.2...3...5....7...37...43...61...67...191...197..1297..1627..1663..1699.=A029974

.7.2...3...5...71..107..157..257..271...307..2549..2647..2801..3347..3697.=A029975

.8.2...3...5....7...73...89...97..113...211...227...251...349...373...463.=A029976

.9.2...3...5....7..109..127..173..191...227...337...373...419...601...619.=A029977

10.2...3...5....7...11..101..131..151...181...191...313...353...373...383.=A002385

11.2...3...5....7..199..277..421..443...499...521...587...643...709...743.=A029978

12.2...3...5....7...11...13..157..181...193...229...241...277...761...773.=A029979

...

inf..2..3..5..7..11..13..17..19..23..29..31..37..41..43..47..53..59..61...=A000040

MAPLE

A230820 := proc(b, n)

    option remember;

    local a, dgs ;

    if n = 1 then

        if b = 2 then

            return 3;

        else

            return 2;

        end if;

    else

        for a from procname(b, n-1)+1 do

            if isprime(a) then

                ispal := true ;

                dgs := convert(a, base, b) ;

                for i from 1 to nops(dgs)/2 do

                    if op(i, dgs) <> op(-i, dgs) then

                        ispal := false;

                    end if;

                end do:

                if ispal then

                    return a;

                end if;

            end if;

        end do:

    end if;

end proc:

for b from 2 to 9 do

    for n from 1 to 9 do

        printf("%3d ", A230820(b, n)) ;

    end do:

    printf("\n") ;

end do; # R. J. Mathar, Feb 16 2014

MATHEMATICA

palQ[n_Integer, base_Integer] := Module[{idn = IntegerDigits[ n, base]}, idn == Reverse@ idn]; Table[Select[Prime@Range@500, palQ[#, k + 1] &][[b - k + 1]], {b, 11}, {k, b, 1, -1}] // Flatten

CROSSREFS

Cf. A000040, A016041, A029971, A029972, A029973, A029974, A029975, A029976, A029977, A002385, A029978, A029979, A029980, A029981, A029982, A029732, A182231.

Sequence in context: A281006 A046227 A120842 * A152178 A274164 A103340

Adjacent sequences:  A230817 A230818 A230819 * A230821 A230822 A230823

KEYWORD

nonn,base,easy,tabl

AUTHOR

Robert G. Wilson v, Oct 30 2013

STATUS

approved

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Last modified August 15 09:12 EDT 2018. Contains 313756 sequences. (Running on oeis4.)