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A056776 Composite numbers k such that phi(k+12) = phi(k) + 12. 1
45, 65, 80, 99, 112, 117, 135, 171, 176, 196, 207, 209, 272, 279, 294, 304, 310, 312, 369, 406, 429, 477, 496, 531, 592, 656, 657, 711, 752, 801, 909, 927, 944, 981, 1014, 1072, 1078, 1179, 1251, 1359, 1424, 1557, 1611, 1629, 1712, 1719, 1744, 1786, 1791 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

There are common cases with A054902.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

EXAMPLE

656 is a term since it is composite and phi(656) = 320, phi(656+12) = phi(668) = 332 = 320 + 12.

657 is a term since it is composite and phi(657) = 432, phi(657+12) = phi(669) = 444 = 432 + 12.

MATHEMATICA

Select[Range[1800], CompositeQ[#] && EulerPhi[# + 12] == EulerPhi[#] + 12 &] (* Amiram Eldar, Mar 01 2020 *)

CROSSREFS

Cf. A000010, A001838, A015917, A054902, A046133, A046133.

Sequence in context: A336553 A140278 A046426 * A172466 A038494 A026043

Adjacent sequences:  A056773 A056774 A056775 * A056777 A056778 A056779

KEYWORD

nonn

AUTHOR

Labos Elemer, Aug 17 2000

STATUS

approved

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Last modified May 7 12:56 EDT 2021. Contains 343650 sequences. (Running on oeis4.)